WO2004001735A1 - Optical recording/reproducing method and optical recording medium - Google Patents

Optical recording/reproducing method and optical recording medium Download PDF

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Publication number
WO2004001735A1
WO2004001735A1 PCT/JP2003/007974 JP0307974W WO2004001735A1 WO 2004001735 A1 WO2004001735 A1 WO 2004001735A1 JP 0307974 W JP0307974 W JP 0307974W WO 2004001735 A1 WO2004001735 A1 WO 2004001735A1
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WO
WIPO (PCT)
Prior art keywords
noble metal
layer
recording
metal oxide
reproduction
Prior art date
Application number
PCT/JP2003/007974
Other languages
French (fr)
Japanese (ja)
Inventor
Takashi Kikukawa
Junji Tominaga
Takayuki Shima
Akihiro Tachibana
Hiroshi Fuji
Jooho Kim
Original Assignee
Tdk Corporation
National Institute Of Advanced Industrial Science And Technology
Pioneer Corporation
Sharp Kabushiki Kaisha
Samsung Japan Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tdk Corporation, National Institute Of Advanced Industrial Science And Technology, Pioneer Corporation, Sharp Kabushiki Kaisha, Samsung Japan Corporation filed Critical Tdk Corporation
Priority to CNA038173441A priority Critical patent/CN1672202A/en
Priority to KR1020047021147A priority patent/KR100658538B1/en
Priority to US10/519,169 priority patent/US20060250916A1/en
Priority to EP03760942A priority patent/EP1555666A4/en
Publication of WO2004001735A1 publication Critical patent/WO2004001735A1/en

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B7/2433—Metals or elements of Groups 13, 14, 15 or 16 of the Periodic Table, e.g. B, Si, Ge, As, Sb, Bi, Se or Te
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045—Recording
    • G11B7/00452—Recording involving bubble or bump forming
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24318—Non-metallic elements
    • G11B2007/2432—Oxygen

Definitions

  • the present invention is near and below the resolution limit determined by light diffraction!
  • the present invention relates to an optical recording Z reproducing method capable of recording and reproducing recording marks having dimensions, and an optical recording medium.
  • a read signal cannot be obtained by reading a recording mark row having an arrangement pitch of less than 0.5 ⁇ and a mark length of less than 0.25 ⁇ / ⁇ . Therefore, in order to read a signal recorded at high density, it is necessary to reduce ⁇ , and ⁇ or
  • Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 980-981 describes a super-resolution technique using near-field light.
  • the optical disc described in this document performs recording and reproduction using near-field light.
  • the recording layer of this optical disk is made of Ge 2 Sb 2 Te 5 which is a phase change material. Therefore, in this optical disc, a crystalline recording mark is formed on the amorphous recording layer.
  • the carrier to noise ratio which is one of the measures of signal strength
  • CNR carrier to noise ratio
  • the read power for generating a probe in the read layer is relatively large, the amorphous phase in the non-mark portion of the recording layer is easily crystallized by the irradiation of the read laser beam. Therefore, repeated reading There is a problem that the recording mark is deteriorated by the recording, that is, the reproduction durability is not sufficient.
  • An object of the present invention is to record a recording mark row including a recording mark smaller than the resolution limit determined by light diffraction, or a recording mark having a size larger than the resolution limit but close to the resolution limit. In such a case, a high reproduction output can be obtained from all the included recording marks, and high reproduction durability can be realized.
  • Recording is performed by irradiating a recording laser beam to the optical recording medium to form a record mark array, and then irradiating one beam of a reproduction laser with a wavelength using an optical system with a numerical aperture of NA.
  • the recording mark row is formed by deformation of the noble metal oxide layer due to decomposition of the noble metal oxide, and includes at least a recording mark having a mark length of less than 0.37 mm / NA.
  • An optical recording Z reproducing method in which noble metal particles are irreversibly deposited in a noble metal oxide layer in which a recording mark array is formed, and the deposited noble metal particles are irradiated with a reproduction laser beam to read the recording mark array.
  • optical recording Z reproducing method according to (1) or (2), wherein the optical recording medium has a first dielectric layer and a second dielectric layer sandwiching the noble metal oxide layer.
  • optical recording medium described above, wherein the optical recording medium has a light absorbing layer mainly composed of a metal and a metal or a metalloid, and the light absorbing layer and the noble metal oxide layer are present so as to sandwich the second dielectric layer.
  • the optical recording medium has a light absorbing layer mainly composed of a metal and a metal or a metalloid, and the light absorbing layer and the noble metal oxide layer are present so as to sandwich the second dielectric layer.
  • optical recording medium has a reflective layer mainly composed of metal and Z or semimetal, and the reflective layer and the light absorbing layer are present so as to sandwich the third dielectric layer.
  • Z playback method
  • FIG. 1A is a sectional view showing the structure of the optical recording medium of the present invention.
  • Fig. 1B and Fig. 1C are each a drawing substitute photograph showing the thin film structure, and are transmission electron micrographs of the cross section of the medium shown in Fig. 1A, and Fig. 1B is reproduced with 1 mW power after recording
  • Fig. 1C shows a photo after recording, which was reproduced with 4 mW power and then reproduced with lmW power.
  • FIG. 2 is a cross-sectional view illustrating a configuration example of the optical recording medium of the present invention.
  • FIG. 3 is a sectional view showing another configuration example of the optical recording medium of the present invention.
  • FIG. 4 is a cross-sectional view showing another configuration example of the optical recording medium of the present invention.
  • FIG. 5 is a cross-sectional view showing another configuration example of the optical recording medium of the present invention.
  • Figure 6 is a graph showing the relationship between mark length and CNR.
  • FIG. 7 is a graph showing the relationship between mark length and CNR.
  • FIG. 8 is a graph showing the relationship between mark length and CNR.
  • FIG. 9 is a graph showing the relationship between the number of times of reproduction and CNR.
  • FIG. 10 is a graph showing the relationship between the number of times of reproduction and CNR.
  • FIG. 11 is a graph showing the relationship between the number of times of reproduction and CNR.
  • FIG. 12 is a graph showing the relationship between the mark length and the CNR.
  • Figure 13 shows the reflection layer thickness and CNR.
  • FIG. 14A is a sectional view showing the structure of the optical recording medium of the present invention.
  • 14B and 14C are each a drawing substitute photograph showing the thin film structure, and are transmission electron micrographs of the cross section of the medium shown in FIG. 14A, and FIG. 14B is reproduced with lmW power after recording.
  • the later photo, Figure 14C shows the photo after recording, with 4 mW power and then with lmW power.
  • FIG. 15 is a graph showing the relationship between mark length and CNR.
  • FIG. 16 is a graph showing the relationship between the mark length and the CNR.
  • the inventors of the present invention use a noble metal oxide layer as a recording layer in a medium having a noble metal oxide layer, and use this layer as a recording mark having a small recording mark smaller than the resolution limit or larger than the resolution limit but at the resolution limit.
  • a high CNR can be obtained in super-resolution reproduction and high reproduction durability can be obtained.
  • FIG. 1A shows a preferred configuration example of an optical recording medium to which the recording / reproducing method of the present invention is applied.
  • a first dielectric layer 31, a noble metal oxide layer 4, a second dielectric layer 32, a light absorbing layer 5, and a third dielectric layer 33 are formed on a substrate (not shown). They are provided in order.
  • the light absorbing layer 5 is composed of a Ag- I n- S b_Te alloy
  • a dielectric layer 31, 32, 33 consists of n SS i 0 2 I have.
  • a laser beam for recording Z reproduction is applied to the noble metal oxide layer 4 and the light absorbing layer 5 through the substrate.
  • the recording laser beam has two power levels: a recording power level (10 mW) and a bias power level (lmW).
  • the intensity is modulated so as to have one level. That is, the recording power was set to 10 mW.
  • reproduction was performed with the reproduction power Pr set to lmW or 4 mW, and the CNR was measured.
  • FIG. 1B shows a transmission electron microscope (TEM) photograph of a cross section of the medium shown in Fig. 1A after reproducing with the reproducing power lmW.
  • FIG. 1C shows a TEM photograph of a cross section of the medium after reproduction at a reproduction power of 4 mW and then reproduction at a reproduction power of lmW.
  • FIG. 14B shows a transmission electron microscope (TEM) photograph of a cross section of the medium shown in FIG. 14A after reproduction at a reproduction power of lmW.
  • FIG. 14C shows a TEM photograph of a cross section of this medium after reproduction at a reproduction power of 4 mW and then reproduction reproduction at lmW.
  • the cross section shown in each of these figures is substantially parallel to the recording track, that is, substantially parallel to the recording mark row.
  • a cavity was formed by the recording beam irradiation in the area where the Ag x layer existed before recording, and that the cross-sectional shape of this cavity fluctuated periodically.
  • the dynamic period corresponds to the recording mark arrangement pitch of 40 Onm. Therefore, in the cavity cross section in Fig. 1B, the convex portion (the region where the cavity height is relatively large) corresponds to the region (recording mark) irradiated with the laser beam at the recording power level, and the concave portion (the cavity height). Is relatively small) is the bias power level. It is thought to correspond to the area (space) where the laser beam was irradiated. Ag particles 40 are slightly precipitated in the cavities.
  • the light absorbing layer 5 was amorphous before recording, but crystallized after recording on the entire area of the recorded track. From FIG. 1C, it can be seen that there is no change in the contour of the cavity formed during recording after reproduction with a power of 4 mW, but the number of Ag particles 40 in the cavity has increased significantly. In other words, it can be seen that Ag particles were precipitated by the reproduction laser beam irradiation. The Ag particles 40 are not uniformly distributed in the cavity. No loss of the reproduced signal due to the non-uniform force distribution was observed.
  • the recording mechanism is first considered. Crystallization of A g O in the noble metal oxide layer 4 made of x, the recording time (the laser beam of the recording power level upon irradiation) A g O x ⁇ A g + x / 2 0 2 decomposition and the light absorbing layer 5 happenss. Oxygen gas generated during recording (0 2) pushes up the second dielectric layer 3 2 and the light absorbing layer 5 with undergo volume expansion in the noble metal oxide layer 4 to deform the noble metal oxide layer 4. Also,
  • the noble metal Sani ⁇ layer 4 made of P t O y Even in the noble metal Sani ⁇ layer 4 made of P t O y, same decomposition occurs. As a result, at the portion irradiated with the laser beam at the recording power level, the second dielectric layer 32 is curved so as to protrude upward in the figure, and the thickness of the light absorbing layer 5 is smaller than the surrounding area, As a result, this portion functions as a recording mark. It is considered that O 2 is enclosed in the formed cavity. Because this mechanism works The, the noble metal oxide is decomposed into noble metal and o 2, that is o 2 generated by the decomposition deforming the noble metal belonging to the genus oxide layer 4, i.e., the second dielectric layer 3 2 and the light absorbing layer 5 deforms Two processes are required.
  • the light absorbing layer 5 made of a typical phase-change recording material is entirely crystallized, so this recording mechanism is based on the difference in the reflectance between crystalline and amorphous. This is different from the recording mechanism in a phase change recording medium that detects a recording mark based on the recording mark.
  • the Ag particles serve as a probe that scatters near-field light, and function similarly to the Ag probe described in Jpn. J. Appl. Phys. Vo 1.39 (2000) pp. 980-981. It is considered that near-field light is converted to propagation light to enable super-resolution reproduction.
  • both the mark length and the space length are as short as 20 O nm, so that the deformation of the noble metal oxide 4 due to the generation of O 2 in the mark also affected the space,
  • the area corresponding to the space is also hollow.
  • the noble metal particles that have been deposited in the cavities of the noble metal oxide layer 4 by laser beam irradiation during reproduction do not disappear even after reproduction. Therefore, it is not necessary to precipitate further noble metal particles during the second and subsequent regenerations.
  • the CNR could not be obtained.
  • the precipitation of the noble metal particles does not need to be performed by irradiation with a reproduction laser beam, and may be performed before the reproduction by irradiating a laser beam for precipitation of the noble metal particles.
  • noble metal particles are slightly precipitated during recording, but the amount of noble metal particles precipitated during recording may be larger.
  • a large amount of noble metal particles precipitate during recording and the precipitation density of noble metal particles almost changes during subsequent laser beam irradiation, such as during reproduction. It is not necessary.
  • the crystal structure and particle size of the noble metal particles precipitated during recording may change during subsequent laser beam irradiation, such as during reproduction.
  • the laser beam incident direction it is preferable to set the laser beam incident direction so that the laser beam transmitted through the noble metal oxide layer 4 is irradiated on the light absorbing layer 5 during recording and super-resolution reproduction.
  • the light absorbing layer 5 may be damaged.
  • the light absorbing layer 5 is formed of a phase-change material and a laser beam is directly applied to the light absorbing layer 5 without passing through the noble metal oxide layer 4, no recording mark is formed on the noble metal oxide layer 4. In some cases, an amorphous or crystalline recording mark is formed on the light absorbing layer 5. In such a case, the recording / reproducing mechanism characteristic of the present invention cannot be realized.
  • the present invention includes a case where the medium does not have the light absorbing layer 5.
  • the laser beam may be incident from any surface of the medium, even during recording and playback, and at the time of deviation.
  • Japanese Patent No. 3157019 discloses and Patent No. 3071243 publication, has a recording layer consisting of silver oxide, voids in the recording layer of silver oxide by recording beam irradiation is decomposed into A g and 0 2 is formed An optical recording medium to be used is described. These optical recording media are similar to the media to which the present invention is applied in that voids are formed in the silver oxide layer during recording.
  • the reproduction laser beam has a wavelength of 78 Onm and a power of 0. Although a 5 mW power is used, Ag particles cannot be precipitated with this level of reproducing power, so super-resolution reproduction is impossible.
  • the laser beam intensity is modulated based on a signal modulated by a data modulation method such as EFM and the medium is irradiated, and a recording mark array including recording marks of various lengths Is formed on the recording track.
  • the present invention has an excellent effect that a high CNR can be obtained when reproducing a recording mark smaller than the resolution limit of 0.25 ⁇ / ⁇ .
  • the CNR improvement effect is realized when reproducing minute recording marks that are larger than the resolution limit but close to the resolution limit.
  • the CNR improvement effect is large when playing back recorded marks whose mark length is less than 0.37 ⁇ / ⁇ , especially 0.28 ⁇ ⁇ / ⁇ or less. Therefore, the present invention is effective when forming a recording mark row including recording marks of such dimensions.
  • the mark length is 0.05 ⁇ or more, particularly 0.09 ⁇ .
  • the present invention it is preferable to apply the present invention to reproduction of a record mark row including the above-mentioned record marks.
  • the present invention at the time of recording, it is necessary to decompose the noble metal oxide to form cavities in the noble metal oxide layer, and to irreversibly precipitate the noble metal particles before reproduction or at least during the first reproduction. If the recording power and / or reproducing power is too low, such a recording / reproducing mechanism will not work sufficiently, and a high CNR cannot be obtained. on the other hand, If the recording power and Z or reproduction power are too high, the durability of the media will be affected and the media may be damaged. Therefore, there is an optimum value for the recording power and the reproduction power.
  • the recording power and the reproducing power may be experimentally determined so as to obtain a high CNR.
  • FIG. 2 shows a configuration example of the optical recording medium of the present invention.
  • This medium has a first dielectric layer 31, a noble metal oxide layer 4, a second dielectric layer 32, a light absorbing layer 5 and a third dielectric layer 33 on a substrate 2 in this order.
  • the noble metal oxide layer 4 contains a noble metal oxide, and is preferably substantially composed of only a noble metal oxide.
  • the noble metal oxide layer may contain two or more kinds of noble metal oxides.
  • the noble metal oxide layer may have a single-layer structure or a stacked structure in which a plurality of layers each containing at least one type of noble metal oxide are stacked.
  • precious money When two or more noble metal oxides are contained in the generic acid layer, not all of the two or more noble metal oxides may be simultaneously decomposed at the time of recording, and at the time of reproduction. All of the precious metals or species may not aggregate at the same time, which may adversely affect recording / reproducing characteristics. Therefore, it is preferable that the noble metal oxide layer contains only one kind of noble metal oxide.
  • the kind of the noble metal used in the present invention is not particularly limited, and the above-described recording / reproducing mechanism functions even when any noble metal is used.
  • the formation of oxide, the stability of the oxide, the visible From the viewpoint of the efficiency of near-field light generation by light, at least one of platinum and silver oxide platinum is preferable, silver silver Z or platinum is more preferable, higher CNR is obtained, and reproduction durability is obtained.
  • platinum oxide is used, and this is represented by P to y , it is preferable to obtain a high CNR when reproducing a minute recording mark.
  • composition of P t O y is involved in the reproduction durability.
  • the composition of P t O y is involved in the reproduction durability.
  • silver oxide when expressed as AgO x , in order to obtain a high CNR when reproducing minute recording marks, it is preferable to use silver oxide.
  • the composition of the noble metal oxide layer 4 can be measured by, for example, X-ray fluorescence analysis.
  • the thickness of the noble metal oxide layer 4 is preferably 1 to 3 Onm, more preferably 2 to 20 nm. If the noble metal oxide layer 4 is too thin, it is difficult to form a continuous film, and it is difficult to obtain stable recording / reproducing characteristics. On the other hand, if the noble metal oxide layer 4 is too thick, a high CNR cannot be obtained.
  • a structure in which the light absorbing layer 5 is removed from FIG. 2 (the structure shown in FIG. 5) is also included in the present invention.
  • the temperature of the noble metal oxide layer 4 is not sufficiently raised during laser beam irradiation, and as a result, it is difficult to obtain a sufficiently high CNR. Therefore, in a structure in which the light absorption layer 5 is not provided, it is preferable that the noble metal oxide layer 4 is thickened to increase the light absorption.
  • Preferred thickness of noble metal oxide layer 4 in this structure Is 20 to 10 O nm. In this case, if the noble metal oxide layer 4 is too thick, the noble metal oxide layer 4 becomes unstable and the reproduction durability tends to decrease.
  • the method for forming the noble metal oxide layer 4 is not particularly limited, and a physical vapor deposition (PVD) such as sputtering or vapor deposition, or a chemical vapor deposition (CVD) can be used. Among them, a reactive sputtering method using a noble metal target and using oxygen as a reaction gas is preferable.
  • PVD physical vapor deposition
  • CVD chemical vapor deposition
  • the light absorbing layer 5 absorbs the laser beam during reproduction and raises the temperature, thereby raising the temperature of the adjacent noble metal oxide layer 4 to promote the noble metal deposition. Since the noble metal oxide layer 4 has high transparency to the laser beam for recording / reproducing Z and is hard to be heated, it is difficult to obtain a sufficiently high CNR unless a light absorbing layer is provided.
  • the light absorption layer 5 is configured to sufficiently raise the temperature by laser beam irradiation.
  • the light absorption layer 5 may have a high absorption coefficient or a low thermal conductivity.
  • the recording mark since the recording mark needs to be formed by forming a cavity by the above-described mechanism, it is preferable that the light absorbing layer 5 be easily deformed so as not to hinder the formation of the cavity.
  • the constituent material of the light absorbing layer 5 is preferably a material mainly composed of a metal or an alloy (including an intermetallic compound) containing one or more elements selected from metals and metalloids.
  • An alloy containing at least Sb and / or Te is preferable because the above properties required for the absorption layer 5 can be easily realized.
  • the element M represents an element excluding S b and Te, respectively, and a and b represent an atomic ratio, preferably 0 ⁇ a ⁇ 1
  • the element M is not particularly limited, but for example, In, Ag, Au, Bi, Se, Al, P, Ge, H, Si, C, V, W, Ta, Zn, T i ⁇ At least one selected from Sn, Pb, Pd and rare earth elements (Sc, Y and lanthanoids) is preferred.
  • alloys having the composition represented by the above formula I include alloys known as phase change recording materials.
  • a phase change recording material is an alloy used as a recording material for a medium for reading a recording mark made of an amorphous or crystalline material by utilizing a difference between a reflectance in a crystalline state and a reflectance in an amorphous state.
  • the light absorbing layer 5 in the present invention is not used as a phase change type recording layer utilizing the difference between the reflectance in a crystalline state and the reflectance in an amorphous state.
  • the light absorbing layer 5 When the light absorbing layer 5 is made of a phase change recording material and is amorphous and only a short recording mark is to be recorded on the noble metal oxide layer 4, the light absorbing layer 5 may be placed on the surface of the light absorbing layer 5 during recording. Due to the thermal diffusion, the light absorption layer 5 is continuously crystallized in the recording track direction, that is, the light absorption layer 5 is crystallized even between the marks (spaces), so that no problem occurs during reproduction. However, when a long space is formed in the noble metal oxide layer 4, the light absorbing layer 5 may remain amorphous near the center of the space. The region that remains amorphous may be crystallized during reproduction, and this crystallization may cause disturbance in the reproduced signal.
  • the entire area of the light absorption layer 5 must be crystallized before recording on the noble metal oxide layer 4. Is preferred. This crystallization can be performed by laser beam irradiation as in the case of the entire crystallization of the recording layer in the phase change medium (initial shading). However, light absorption In the crystallization treatment of the layer 5, it is necessary to set processing conditions so that the noble metal oxide does not decompose in the noble metal oxide layer 4.
  • the thickness of the light absorbing layer 5 is too small, it is difficult to secure a sufficient light absorption rate, and if the thickness is too large, it is difficult to deform during recording, so it is preferably 2 to 200 nm, more preferably 1 to 200 nm. 0 to: 10 O nm.
  • the method for forming the light absorbing layer 5 is not particularly limited, and the above-described PVD method or CVD method can be used.
  • the first dielectric layer 31 is provided to protect the substrate 2 by dissipating heat transmitted from the noble metal oxide layer 4 in the in-plane direction during recording Z reproduction, and to control the reflectance of the medium.
  • the second dielectric layer 32 is provided for protecting the CNR and protecting the noble metal oxide layer 4.
  • the third dielectric layer 33 is provided to protect the light absorbing layer 5. Since the second dielectric layer 32 needs to be deformed along with the formation of a cavity in the noble metal oxide layer 4 during recording, it is preferable that the second dielectric layer 32 be configured to be easily deformed.
  • each dielectric layer may be appropriately determined so that its function is sufficiently exhibited.
  • 1 output Normally, the first dielectric layer 31 has a thickness of 10 to 30 O nm, and the second dielectric layer has a thickness of 10 to 30 O nm. 32 is 5 nm or more and less than 100 nm, preferably 10 to 60 nm, and the third dielectric layer 33 is preferably 10 to 200 nm. If the second dielectric layer 32 is too thick or too thin, the CNR during super-resolution reproduction will be low.
  • each dielectric layer for example, various compounds containing at least one metal component or metalloid component selected from Si, Ge, Zn, A, and rare earth elements are preferable.
  • the compound is preferably an oxide, a nitride or a sulfide, and a mixture containing two or more of these compounds can also be used.
  • nitride such as silicon nitride must be used. Is not preferred.
  • a resin protective layer may be provided on the third dielectric layer 33 for the purpose of protecting the medium.
  • the light absorbing layer 5 is made of a phase change material, it is preferable to provide the third dielectric layer 33. However, it is not essential to provide the third dielectric layer 33, and the light absorbing layer 5 is not necessary. , A resin protective layer may be formed.
  • the method for forming these dielectric layers is not particularly limited, and the above-described PVD method or CVD method can be used.
  • Board 2
  • the substrate 2 is provided to maintain the rigidity of the medium.
  • the thickness of the substrate 2 may be generally from 0.2 to 1.2 thighs, preferably from 0.4 to 1.2.
  • the substrate 2 is usually provided with a group (guide groove) for tracking.
  • the layers from the first dielectric layer 31 to the third dielectric layer 33 may be laminated on the substrate in the reverse order of the lamination shown in FIG.
  • the substrate 2 When a laser beam is incident on the medium from the substrate 2 side, the substrate 2 is made of a translucent material.
  • the constituent material of the substrate 2 may be selected from various materials such as resin, glass, metal, and ceramic according to the required rigidity and transparency.
  • the medium shown in FIG. 3 has a structure in which a reflective layer 6 is provided on the third dielectric layer 33 of the medium shown in FIG.
  • the reflective layer 6 is provided, the laser beam for recording / reproducing Z is made incident on the medium from the lower side in the figure.
  • the reproduction output of a recording mark having a mark length larger than the resolution limit can be improved.
  • all light passing through the interface between the light absorption layer 5 and the third dielectric layer 33 is transmitted to the outside of the medium. So Therefore, the CNR does not increase for recording marks that are read out by detecting the reflection of propagating light without using near-field light, that is, recording marks that are sized to allow normal reproduction instead of super-resolution reproduction.
  • the reflection layer 6 is provided, the interference effect between the light reflected at the interface between the third dielectric layer 33 and the reflection layer 6 and the light reflected at the other interface can be used, so that the propagation It is thought that the CNR of a recording mark of a size that can be reproduced only by light increases.
  • the thickness of the reflection layer 6 when the thickness of the reflection layer 6 is increased, the intensity of the transmitted light that is reflected by the reflection layer 6 and returns to the optical pickup increases, and as a result, the propagation light that is converted from the near-field light and returned to the optical pickup in the noble metal oxide layer 4 Since the intensity is relatively low, the CNR of the minute recording mark that is the subject of super-resolution reproduction will be low. Therefore, it is preferable to set the thickness of the reflective layer 6 so that sufficient CNR can be obtained for both large recording marks and minute recording marks. Specifically, it may be determined experimentally according to the material constituting the reflective layer 6, but it is usually preferably 1 to 100 nm, particularly preferably 2 to 15 nm.
  • the reflective layer 6 is made of a single metal or semimetal such as Al, Au, Ag, Pt, Cu, Ni, Cr, Ti, Si, or an alloy containing two or more metals or semimetals. It may be configured.
  • the method for forming the reflective layer 6 is not particularly limited, and the above-described PVD method or CVD method can be used.
  • Media structure shown in Fig. 4
  • the medium shown in FIG. 4 has a structure in which the precipitation promoting layer 7 is provided between the first dielectric layer 31 and the noble metal oxide layer 4 of the medium shown in FIG.
  • the precipitation temperature of the noble metal particles during regeneration changes.
  • a reproduction power for super-resolution reproduction is required. The lower the one, the better. Therefore, it is preferable to provide a layer having a function of lowering the precipitation temperature of the noble metal particles in contact with the noble metal oxide layer 4.
  • This layer is preferably thick enough to not impair the overall optical design and thermal balance of the media.
  • the precipitation accelerating layer 7 is a layer having a function of improving the reproduction sensitivity as described above. By providing this layer, the same CNR can be obtained with a lower reproduction power as compared with the case where no such layer is provided.
  • the precipitation promoting layer 7 is preferably made of, for example, silicon nitride, and preferably has a thickness of 2 to 2 O nm.
  • the method for forming the precipitation promoting layer 7 is not particularly limited, and the above-described PVD method or CVD method can be used.
  • the reflection layer 6 shown in FIG. 3 and the precipitation promoting layer 7 shown in FIG. 4 may be provided together.
  • the medium shown in FIG. 5 has a structure in which the light absorbing layer 5 and the third dielectric layer 33 are removed from the medium shown in FIG.
  • An optical disk evaluation device (DDU1000 manufactured by Pulstec) was installed. The linear velocity during recording and playback was 6 m / s.
  • the laser beam emitted from the low-resolution pickup enters the noble metal oxide layer 4 from the substrate side, and the laser beam emitted from the high-resolution pickup is emitted from the opposite side of the substrate from the noble metal oxide.
  • the high-resolution pickup corresponds to normal reproduction.
  • Example 11 Structure of FIG. 2: Noble metal oxide A g O x )
  • an optical disk sample having a laminated structure composed of a substrate 2 Z first dielectric layer 31 Z noble metal oxide layer 4 / second dielectric layer 32 / light absorbing layer 5 Z third dielectric layer 33 is formed. did.
  • the thickness in parentheses is the thickness.
  • the ZnS—Si 2 layer was formed by sputtering a target having a composition represented by a molar ratio of (Zn S) 85 (Si 2 ) 15 in an Ar atmosphere.
  • X in the formed AgO x was 1.
  • Ag- I n- S b-T e layer, A g 6 .. I n 4. 5 S b 6 . . 8 T e 28. 7 (molar 0 / o) targets were formed by sputtering-ring in A r atmosphere.
  • the light absorption layer 5 was irradiated by continuously irradiating the recording target track with a 1.2 mW laser beam for 3 seconds with a low-resolution pickup while rotating the sample at a linear velocity of 6 m / s. Crystallized. Unless otherwise specified, in the following examples, the light absorption layer 5 was crystallized before evaluating the recording / reproducing characteristics in the same manner as in this example.
  • composition of the light absorbing layer 5 (molar ratio) G e 2 S b 2 T e 5 or (S b .. 7 Te., 3) 0. 95 even when the G e 0. 05, almost the same The result was obtained.
  • Example 11 A sample was prepared in the same manner as in Example 1. However, the light absorbing layer 5 was not crystallized.
  • a laser beam is applied to this sample from the third dielectric layer 33 side using a high-resolution pickup, and a recording mark array with an arrangement pitch of 400 nm (mark length of 200 nm) is recorded at a recording power of 6 mW. And reproduced with a power of 0.7 mW using a high-resolution pickup, a CNR of 44 dB was obtained.
  • the noble metal oxide constituting the noble metal oxide layer 4 is preferably a platinum oxide.
  • FIG. 14A, FIG. 14B, and FIG. 14C are sample cross-sectional photographs in an experiment in which recording / reproduction was performed under the same conditions as in this example. However, in the experiment, the light absorbing layer 5 was not crystallized before recording.
  • Example 11 Structure of FIG. 2: Noble metal oxide P d O z )
  • the noble metal oxide layer 4 in Example 1-1 to prepare a sample was changed to P dO z (4nm).
  • Z in P d ⁇ z was 1.10.
  • Example 1-2 by controlling the flow rate ratio A r / ⁇ 2 upon P t O y layer is formed to prepare a plurality of samples having different P t O y layer of y.
  • the ratio between the value of y and the flow rate (unit: sccm) in each sample is
  • Example 1 In the structure of Example 1 one 3, by controlling the flow rate ratio A r / ⁇ 2 upon P d Ojl formed, plural samples were prepared having different P DOji of z. The ratio between the value of z and the flow rate (unit: sccm) for each sample is
  • Example 1-6 (the structure of Figure 2: Comparison with P T_ ⁇ y layer and A g O x layer)
  • a recording mark array with an array pitch of 40 Onm (mark length of 20 Onm) was recorded under optimum conditions, and the CNR was measured by reproducing with a 4 mW reproduction power using a low-resolution pickup. Relationship between the thickness and the CNR of P t O y layer of each sample, "thickness: CNR" expressed in the form of,
  • the noble metal oxide layer 4 made of P dO z formed under the condition that the z 1. 10, 2 ⁇ its thickness: addition to vary within the range of 15 nm in the same manner as in Example 15 sample was prepared.
  • a recording mark array with an array pitch of 30 Onm was recorded on each of these samples under the optimum conditions, and reproduced using a high-resolution pickup at a playback power of 4 mW.
  • the CNR was measured.
  • the relationship between the P (10 2 layer thickness and CNR of each sample is expressed as “thickness: CNR”.
  • Example 11-9 structure of FIG. 2: comparison with constituent materials of light absorbing layer 5
  • a recording mark having a recording power of 9 mW and an arrangement pitch of 40 Onm (mark length of 20 On m) was formed on a sample prepared in the same manner as in Example 1-1 except that the light absorption layer 5 was composed of Si, Au or W.
  • the relationship between the light absorbing layer 5 constituent material and CNR was:
  • Example 11 A sample fabricated in the same manner as in Example 11 except that the second dielectric layer 32 was made of silicon nitride was used. At a recording power of 14 mW, an array pitch of 400 nm (mark length of 200 nm) ) was recorded and played back at a playback power of 4 mW using a low-resolution pickup, but no CNR was obtained.
  • Nitride Keimoto are the material much harder than the Z n S- S I_ ⁇ 2 used in Example 1-1, A g O ⁇ 2 produced by the decomposition of x function as a recording mark It is considered that a cavity could not be formed in the noble metal oxide layer 4.
  • Example 1 1 1 1 (Structure of FIG. 2: Comparison based on film thickness of second dielectric layer 32)
  • Example 1-1 The same procedure as in Example 1-1 was carried out except that the thickness of the second dielectric layer 32 was 10 O nm. A sample was prepared. When a recording mark array with an array pitch of 40 Onm (mark length of 200 nm) was recorded on this sample at a recording power of 1 lmW, and reproduced with a reproduction power of 4 mW using a low-resolution pickup, no CNR was obtained. Was.
  • Example 2-1 (Structure of FIG. 3: Effect of the reflective layer 6)
  • Example 1 An Ag layer or A1 layer having a thickness of 1 Onm was formed as a reflective layer 6 on the third dielectric layer 33 of the sample prepared in Example 1 to obtain a sample having the structure shown in FIG. I got The Ag layer and the A1 layer were formed by sputtering an Ag target and an A1 target in an Ar atmosphere, respectively.
  • FIG. 12 shows the results of forming recording mark arrays of ⁇ 1.6 ⁇ (mark length 200 to 80 Onm) and reproducing them with a reproduction power of 4 mW using a low-resolution pickup.
  • FIG. 12 also shows the result of a sample in which the reflective layer 6 was not provided.
  • Example 2-2 structure in FIG. 3: comparison based on thickness of reflective layer 6)
  • Example 3 A sample was produced in the same manner as in Example 2-1 except that the reflective layer 6 had the thickness shown in FIG. For these samples, a record mark array with an array pitch of 40 Onm (mark length 20 Onm) was recorded at the optimum recording power for each, and the results were reproduced at a reproduction power of 4 mW using a low-resolution pickup. See Figure 3.
  • the composition of the silicon nitride layer was Si 3 N 4 .
  • Example 4 (Structure of FIG. 5: Structure without light absorption layer 5)
  • an optical disc sample having a laminated structure composed of the substrate 2 / first dielectric layer 31Z noble metal oxide layer 4 / second dielectric layer 32 was formed.
  • This sample has a structure in which the light absorption layer 5 and the third dielectric layer 33 are removed from the sample of Example 1-1.
  • the thickness of the noble metal oxide layer 4 was set to 18 ⁇ 1 or 60 ⁇ ! 1.
  • a recording mark array with an array pitch of 40 Onm (mark length 20 Onm) was recorded with a recording power of 5 to 14 mW on a sample with a thickness of the noble metal oxide layer 4 of 18 nm. When played back at mW playback speed, no CNR was obtained.
  • a recording mark sequence with an array pitch of 1.6 ⁇ (mark length 80 Onm) was recorded on this sample at a recording power of 14 mW, and was reproduced with a reproduction power of 4 mW. At that time, a CNR of 34 dB was obtained.
  • a recording mark array with an array pitch of 40 Onm (mark length 20 Onm) was recorded at a recording power of 7 mW, and a low-resolution pickup When the data was reproduced with a reproduction power of 4 mW by using, a CNR of 12 dB was obtained.
  • a recording mark array with an array pitch of 1.6 ⁇ (mark length 80 Onm) was recorded on this sample with a recording power of 7 mW, and was reproduced with a reproduction power of 4 mW using a low-resolution pickup.
  • a CNR of 33 dB was obtained.
  • the reason why the CNR could not be obtained or became lower in super-resolution reproduction is considered to be as follows. First, since normal reproduction is possible, it is considered that during recording, the noble metal layer 4 absorbed the laser beam and rose in temperature, and Ag O x was decomposed into Ag and O 2 to form a recording mark. Can be After recording, there was almost no AgO x in the noble metal oxide layer 4 and there was no layer in the medium responsible for absorbing the laser beam. Also, it is considered that the temperature of the noble metal oxide layer 4 was insufficiently increased, and the Ag particles hardly precipitated or did not sufficiently precipitate. It is considered that super-resolution reproduction became possible when the noble metal oxide layer 4 was thickened because the amount of light absorption of the noble metal oxide layer 4 increased.

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Abstract

A recorded mark row is formed on an optical recording medium having a noble metal oxide layer by deforming the noble metal oxide layer by the decomposition of the noble metal oxide. A recorded mark row is read by irreversibly depositing noble metal particles in a recorded mark row-formed noble metal oxide layer and irradiating the deposited noble metal particles with a reproducing laser beam. When the wavelength of a reproducing laser beam is λ, the numerical aperture of a laser beam irradiation optical system NA, a recorded mark row includes at least recorded marks having a mark length of less than 0.37 λ/NA. When recording/reproducing a recorded mark row including recorded marks with sizes smaller than a resolution limit or close to the resolution limit although larger than it, a high reproduction output is obtained and a high reproduction resistance is realized in all the recorded marks included.

Description

光記録/再生方法およぴ光記録媒体 技術分野 Optical recording / reproducing methods and optical recording media
本発明は、 光の回折によって決定される解像限界近傍およびこの解像限界より も小さ！/、寸法をもつ記録マークの記録およぴ再生が可能な光記録 Z再生方法と、 光記録媒体とに関する。 背景技術  The present invention is near and below the resolution limit determined by light diffraction! The present invention relates to an optical recording Z reproducing method capable of recording and reproducing recording marks having dimensions, and an optical recording medium. Background art
通常、 レーザービームを用いた再生方法では、 光の回折によって決定される解 像限界が存在する。 この解像限界は、 レーザービームの波長; Lとレンズの開口数 NAとによって決定される。 カットオフ空間周波数は 2 ΝΑΖλなので、 記録マ ークの長さと、 隣接する 2つの記録マーク間にあるスペースの長さとが同じであ る記録マーク列は、 その空間周波数が 2ΝΑ/λ (ラインペア/ nm) 以下であれ ば読み取り可能である。 この場合、 読み取り可能な空間周波数に対応するマーク 長 （=スペース長） は、  Normally, a reproduction method using a laser beam has a resolution limit determined by diffraction of light. This resolution limit is determined by the wavelength of the laser beam; L and the numerical aperture NA of the lens. Since the cut-off spatial frequency is 2 ΝΑΖλ, a recording mark row whose recording mark length is the same as the length of the space between two adjacent recording marks has a spatial frequency of 2ΝΑ / λ (line pair / nm) is readable. In this case, the mark length (= space length) corresponding to the readable spatial frequency is
λ/4ΝΑ=0. 25 λ/ΝΑ  λ / 4ΝΑ = 0.25 λ / ΝΑ
となる。 すなわち、 配列ピッチ 0. 5 λΖΝΑ未満、 マーク長 0. 25 λ/ΝΑ 未満の記録マーク列を読み出して再生信号を得ることはできない。 したがって、 高密度に記録された信号を読み出すためには、 λを小さくする、 および Ζまたは、Becomes That is, a read signal cannot be obtained by reading a recording mark row having an arrangement pitch of less than 0.5λΖΝΑ and a mark length of less than 0.25λ / ΝΑ. Therefore, in order to read a signal recorded at high density, it is necessary to reduce λ, and Ζ or
Ν Αを大きくすることが有効であり、 これらに関して多くの技術的検討が行われ ている。 It is effective to increase Ν, and many technical studies are being conducted on these.
—方、 解像限界をより小さくしょうとする検討とは別に、 解像限界より小さい 記録マークを読み出すための技術として、 様々な超解像再生技術が提案されてい る。 超解像再生技術としては、 たとえば、 レーザー照射によって開口等を生じる 機能を有する層を媒体内に設けることによって、 媒体内で実質的に NAを高める 技術が提案されている。 —Aside from studying to reduce the resolution limit, various super-resolution reproduction technologies have been proposed as technologies for reading recording marks smaller than the resolution limit. You. As a super-resolution reproduction technology, for example, a technology has been proposed in which a layer having a function of generating an opening or the like by laser irradiation is provided in a medium to substantially increase NA in the medium.
また、 たとえば Jpn. J. Appl. Phys. Vol.39 (2000) pp.980- 981には、 近接場光を利 用した超解像技術が記載されている。 この文献に記載されている光ディスクは、 近接場光を用いて記録および再生が行われる。 この光ディスクは、 記録 Z再生光 入射側から、 ポリカーボネート基板、 厚さ 1 7 Onmの Z n S— S i 02層、 厚さ 15nmの Ag Ox層 （読み出し層） 、 厚さ 4 Onmの Z n S— S i〇2層、 厚さ 1 5 nmの G e2S b2T eji (記録層） および厚さ 20 nmの Z n S— S i 02層をこの 順で積層した構造をもつ。 この光ディスクにおける記録層は、 相変化材料である G e2S b2T e5からなる。 そのためこの光ディスクでは、 非晶質の記録層に結晶 質記録マークを形成することになる。 In addition, for example, Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 980-981 describes a super-resolution technique using near-field light. The optical disc described in this document performs recording and reproduction using near-field light. The optical disc, the recording Z reproducing light incident side, a polycarbonate substrate, Z n S- S i 0 2 layer having a thickness of 1 7 onm, thickness 15 nm Ag O x layer (reading layer), thickness 4 onm of Z n S- S I_〇 two layers, the thickness of 1 5 nm of G e 2 S b 2 T eji (recording layer) and Z n S- S i 0 2 layers of 20 nm thick were laminated in this order Have. The recording layer of this optical disk is made of Ge 2 Sb 2 Te 5 which is a phase change material. Therefore, in this optical disc, a crystalline recording mark is formed on the amorphous recording layer.
上記文献では、 解像限界より小さい記録マークを記録し、 記録後に AgOx層 にレーザービームを照射することによって、 §03£を §と〇2とに分解して A gプローブを生成し、 この A gプローブの周囲に近接場光を発生させることによ り、 記録マークを読み出している。 再生後にレーザービームが移動すると、 Ag および 02は再び AgOxに戻る。 すなわち、 A gプローブの生成は可逆的である。 実際にこの技術を用いることにより、 レーザー波長; L = 635 nm、 開口数 NA = 0. 60の光学系 （解像限界ピッチ 530 nm、 解像限界マーク長 265 nm) を用 レ、、 マーク長 20 Onmのマーク列の読み出しに成功している。 このときの読み出 しパワーは 2. 5mWであり、 線速度は 6. 0m/sである。 しかし、 この超解像再 生技術では、 信号強度の尺度の一つである carrier to noise ratio (CNR) が 小さく実用レベルではない。 また、 読み出し層にプローブを生成するための読み 出しパワーが比較的大きいため、 読み出し用のレーザービームの照射によって記 録層の非マーク部のアモルファス相が結晶化しやすい。 そのため、 繰り返し読み 出しにより記録マークが劣化する、 すなわち再生耐久"生が十分ではない、 という 問題を抱えている。 発明の開示 In the above document, record the resolution limit smaller recording marks by irradiating a laser beam to the AgO x layer after recording, to generate the A g probe decomposed § 0 3 £ to the § and 〇 2, The recording mark is read by generating near-field light around the Ag probe. When the laser beam moves after playing, Ag and 0 2 returns again AgO x. That is, the generation of the Ag probe is reversible. By using this technology, the laser wavelength; L = 635 nm, numerical aperture NA = 0.60 optical system (resolution limit pitch 530 nm, resolution limit mark length 265 nm) Reading of the 20 Onm mark string was successful. The read power at this time is 2.5 mW, and the linear velocity is 6.0 m / s. However, in this super-resolution reproduction technology, the carrier to noise ratio (CNR), which is one of the measures of signal strength, is small and not practical. In addition, since the read power for generating a probe in the read layer is relatively large, the amorphous phase in the non-mark portion of the recording layer is easily crystallized by the irradiation of the read laser beam. Therefore, repeated reading There is a problem that the recording mark is deteriorated by the recording, that is, the reproduction durability is not sufficient.
本発明の目的は、 光の回折によって決定される解像限界より小さい記録マーク、 または、 解像限界以上ではあるが解像限界に近い寸法をもつ記録マークを含む記 録マーク列を記録 z再生する際に、 含まれる全ての記録マークにおいて高い再生 出力が得られ、 かつ、 高い再生耐久性を実現することである。  An object of the present invention is to record a recording mark row including a recording mark smaller than the resolution limit determined by light diffraction, or a recording mark having a size larger than the resolution limit but close to the resolution limit. In such a case, a high reproduction output can be obtained from all the included recording marks, and high reproduction durability can be realized.
上記目的は下記 （1 ) 〜 （8 ) の本発明によって達成される。  The above object is achieved by the present invention described in the following (1) to (8).
( 1 ) 光記録媒体に対し、 記録レーザービームを照射して記録マーク列を形 成することにより記録を行レ、、 開口数 NAの光学系を用いて波長えの再生レーザ 一ビームを照射して記録マーク列を読み出すことにより再生を行う方法であって、 光記録媒体は、 貴金属酸化物を含有する貴金属酸化物層を有し、  (1) Recording is performed by irradiating a recording laser beam to the optical recording medium to form a record mark array, and then irradiating one beam of a reproduction laser with a wavelength using an optical system with a numerical aperture of NA. A method for performing reproduction by reading out a record mark row by using a noble metal oxide layer containing a noble metal oxide,
記録マーク列は、 貴金属酸化物の分解によって貴金属酸化物層が変形すること により形成されたものであり、 マーク長が 0 . 3 7え /N A未満である記録マー クを少なくとも含み、  The recording mark row is formed by deformation of the noble metal oxide layer due to decomposition of the noble metal oxide, and includes at least a recording mark having a mark length of less than 0.37 mm / NA.
記録マーク列が形成されている貴金属酸化物層において貴金属粒子を不可逆的 に析出させ、 析出した貴金属粒子に再生レーザービームを照射することにより記 録マーク列を読み出す光記録 Z再生方法。  An optical recording Z reproducing method in which noble metal particles are irreversibly deposited in a noble metal oxide layer in which a recording mark array is formed, and the deposited noble metal particles are irradiated with a reproduction laser beam to read the recording mark array.
( 2 ) 貴金属酸化物層に銀酸化物、 白金酸化物およびパラジウム酸化物の少 なくとも 1種が含有される上記 （1 ) の光記録/再生方法。  (2) The optical recording / reproducing method according to (1), wherein the noble metal oxide layer contains at least one of silver oxide, platinum oxide and palladium oxide.
( 3 ) 光記録媒体が、 貴金属酸化物層を挟むように第 1誘電体層および第 2 誘電体層を有する上記 （1 ) または （2 ) の光記録 Z再生方法。  (3) The optical recording Z reproducing method according to (1) or (2), wherein the optical recording medium has a first dielectric layer and a second dielectric layer sandwiching the noble metal oxide layer.
( 4 ) 光記録媒体が金属およびノまたは半金属を主成分とする光吸収層を有 し、 光吸収層と貴金属酸化物層とが第 2誘電体層を挟むように存在する上記 (3) の光記録/再生方法。 (4) The optical recording medium described above, wherein the optical recording medium has a light absorbing layer mainly composed of a metal and a metal or a metalloid, and the light absorbing layer and the noble metal oxide layer are present so as to sandwich the second dielectric layer. (3) Optical recording / reproducing method.
(5) 光吸収層が少なくとも S bおよび Zまたは Teを含有する上記 （4) の光記録/再生方法。  (5) The optical recording / reproducing method according to (4), wherein the light absorbing layer contains at least Sb and Z or Te.
( 6 ) 光記録媒体が第 3誘電体層を有し、 第 3誘電体層と第 2誘電体層とが 光吸収層を挟むように存在する上記 （4) または （5) の光記録 Z再生方法。  (6) The optical recording system according to (4) or (5), wherein the optical recording medium has a third dielectric layer, and the third dielectric layer and the second dielectric layer are present so as to sandwich the light absorbing layer. Playback method.
( 7 ) 光記録媒体が金属および Zまたは半金属を主成分とする反射層を有し、 反射層と光吸収層とが第 3誘電体層を挟むように存在する上記 (6) の光記録 Z 再生方法。  (7) The optical recording of (6) above, wherein the optical recording medium has a reflective layer mainly composed of metal and Z or semimetal, and the reflective layer and the light absorbing layer are present so as to sandwich the third dielectric layer. Z playback method.
(8) 貴金属酸ィヒ物を含有する貴金属酸ィヒ物層を有し、 前記貴金属酸化物が 白金酸化物および/またはパラジゥム酸化物である光記録媒体。 図面の簡単な説明  (8) An optical recording medium having a noble metal oxide layer containing a noble metal oxide, wherein the noble metal oxide is platinum oxide and / or palladium oxide. BRIEF DESCRIPTION OF THE FIGURES
図 1Aは、 本発明の光記録媒体の構造を示す断面図である。 図 1 Bおよび図 1 Cはそれぞれ薄膜構造を示す図面代用写真であって、 図 1 Aに示す媒体の断面の 透過型電子顕微鏡写真であり、 図 1 Bは、 記録後に 1 mWのパワーで再生した後の 写真、 図 1 Cは、 記録後に 4 mWのパワーで再生し、 次いで lmWのパワーで再生し た後の写真である。 図 2は、 本発明の光記録媒体の構成例を示す断面図である。 図 3は、 本発明の光記録媒体の他の構成例を示す断面図である。 図 4は、 本発 明の光記録媒体の他の構成例を示す断面図である。 図 5は、 本発明の光記録媒体 の他の構成例を示す断面図である。 図 6は、 マーク長と CNRとの関係を示すグ ラフである。 図 7は、 マーク長と CNRとの関係を示すグラフである。 図 8は、 マーク長と CNRとの関係を示すグラフである。 図 9は、 再生回数と CNRとの 関係を示すグラフである。 図 10は、 再生回数と CNRとの関係を示すグラフで ある。 図 1 1は、 再生回数と CNRとの関係を示すグラフである。 図 12は、 マ ーク長と CNRとの関係を示すグラフである。 図 1 3は、 反射層の厚さと CNR との関係を示すグラフである。 図 14 Aは、 本発明の光記録媒体の構造を示す断 面図である。 図 14 Bおよび図 14 Cはそれぞれ薄膜構造を示す図面代用写真で あって、 図 14 Aに示す媒体の断面の透過型電子顕微鏡写真であり、 図 14 Bは、 記録後に lmWのパワーで再生した後の写真、 図 14Cは、 記録後に 4mWのパワー で再生し、 次いで lmWのパワーで再生した後の写真である。 図 15は、 マーク長 と CNRとの関係を示すグラフである。 図 16は、 マーク長と CNRとの関係を 示すグラフである。 発明を実施するための最良の形態 FIG. 1A is a sectional view showing the structure of the optical recording medium of the present invention. Fig. 1B and Fig. 1C are each a drawing substitute photograph showing the thin film structure, and are transmission electron micrographs of the cross section of the medium shown in Fig. 1A, and Fig. 1B is reproduced with 1 mW power after recording Fig. 1C shows a photo after recording, which was reproduced with 4 mW power and then reproduced with lmW power. FIG. 2 is a cross-sectional view illustrating a configuration example of the optical recording medium of the present invention. FIG. 3 is a sectional view showing another configuration example of the optical recording medium of the present invention. FIG. 4 is a cross-sectional view showing another configuration example of the optical recording medium of the present invention. FIG. 5 is a cross-sectional view showing another configuration example of the optical recording medium of the present invention. Figure 6 is a graph showing the relationship between mark length and CNR. FIG. 7 is a graph showing the relationship between mark length and CNR. FIG. 8 is a graph showing the relationship between mark length and CNR. FIG. 9 is a graph showing the relationship between the number of times of reproduction and CNR. FIG. 10 is a graph showing the relationship between the number of times of reproduction and CNR. FIG. 11 is a graph showing the relationship between the number of times of reproduction and CNR. FIG. 12 is a graph showing the relationship between the mark length and the CNR. Figure 13 shows the reflection layer thickness and CNR. 6 is a graph showing a relationship with the graph. FIG. 14A is a sectional view showing the structure of the optical recording medium of the present invention. 14B and 14C are each a drawing substitute photograph showing the thin film structure, and are transmission electron micrographs of the cross section of the medium shown in FIG. 14A, and FIG. 14B is reproduced with lmW power after recording. The later photo, Figure 14C, shows the photo after recording, with 4 mW power and then with lmW power. FIG. 15 is a graph showing the relationship between mark length and CNR. FIG. 16 is a graph showing the relationship between the mark length and the CNR. BEST MODE FOR CARRYING OUT THE INVENTION
本発明の発明者らは、 貴金属酸化物層を有する媒体において、 貴金属酸化物層 を記録層として用い、 この層に解像限界より小さい微小な記録マークまたは解像 限界より大きいが解像限界に近い微小な記録マークを記録し、 閾値以上の再生パ ヮ一で再生を行うことによって、 超解像再生において高い CNRが得られ、 かつ、 高い再生耐久性が得られることを見いだした。  The inventors of the present invention use a noble metal oxide layer as a recording layer in a medium having a noble metal oxide layer, and use this layer as a recording mark having a small recording mark smaller than the resolution limit or larger than the resolution limit but at the resolution limit. We have found that by recording a very small recording mark and performing reproduction at a reproduction level equal to or higher than the threshold, a high CNR can be obtained in super-resolution reproduction and high reproduction durability can be obtained.
図 1 Aに、 本発明の記録 Z再生方法が適用される光記録媒体の好ましい構成例 を示す。 この光記録媒体は、 基板 （図示せず） 上に、 第 1誘電体層 31、 貴金属 酸化物層 4、 第 2誘電体層 32、 光吸収層 5およぴ第 3誘電体層 33をこの順で 設けたものである。 貴金属酸化物層 4は AgOx (x = l) から構成し、 光吸収 層 5は Ag— I n— S b_Te合金から構成し、 誘電体層 31、 32、 33は n S-S i 02から構成してある。 記録 Z再生のためのレーザービームは、 基板 を通して貴金属酸化物層 4および光吸収層 5に照射される。 FIG. 1A shows a preferred configuration example of an optical recording medium to which the recording / reproducing method of the present invention is applied. In this optical recording medium, a first dielectric layer 31, a noble metal oxide layer 4, a second dielectric layer 32, a light absorbing layer 5, and a third dielectric layer 33 are formed on a substrate (not shown). They are provided in order. Noble metal oxide layer 4 is composed of AgO x (x = l), the light absorbing layer 5 is composed of a Ag- I n- S b_Te alloy, a dielectric layer 31, 32, 33 consists of n SS i 0 2 I have. A laser beam for recording Z reproduction is applied to the noble metal oxide layer 4 and the light absorbing layer 5 through the substrate.
この媒体の特定の記録トラックに対し、 開口数 NA=0. 60の光学系を用い て波長 λ = 635nmの記録レーザービームを照射することにより、 配列ピッチ 4 0 Onm (マーク長 200nm) の記録マーク列を記録した。 記録レーザービームは、 記録パワーレベル ( 10 mW) およびバイアスパワーレベル ( lmW) の 2種のパヮ 一レベルをもつように強度変調したものである。 すなわち、 記録パワーは 10mW とした。 次いで、 再生パワー P rを lmWまたは 4mWとして再生を行い、 CNRを 測定した。 その結果、 再生パワー lmWでは CNRが得られなかったが、 再生パヮ 一 4mWで 4 ldBという高い CNRが得られた。 この場合、 解像限界ピッチが 53 Onm、 解像限界マーク長が 265nmなので、 本発明により、 超解像再生において 従来にない高 C N Rが得られたことがわかる。 By irradiating a specific recording track of this medium with a recording laser beam with a wavelength λ = 635 nm using an optical system with a numerical aperture NA = 0.60, recording marks with an array pitch of 40 Onm (mark length 200 nm) Recorded columns. The recording laser beam has two power levels: a recording power level (10 mW) and a bias power level (lmW). The intensity is modulated so as to have one level. That is, the recording power was set to 10 mW. Next, reproduction was performed with the reproduction power Pr set to lmW or 4 mW, and the CNR was measured. As a result, a CNR could not be obtained at a reproduction power of lmW, but a high CNR of 4 ldB was obtained at a reproduction power of 4 mW. In this case, since the resolution limit pitch is 53 Onm and the resolution limit mark length is 265 nm, it can be seen that the present invention has achieved an unprecedentedly high CNR in super-resolution reproduction.
図 14 Aに示す媒体は、 貴金属酸化物層 4を P t Oy (y = 2) から構成した ほかは図 1 Aに示す媒体と同じ構成である。 この媒体に対し、 記録パワーレベル を 10. 5 mWに変更したほかは図 1 Aに示す媒体と同条件で記録を行い、 CNR を測定した。 その結果、 再生パワー lmWでは CNRが得られなかったが、 再生パ ヮー 4 mWで 40 dB以上の C N Rが得られた。 The medium shown in FIG. 14A has the same configuration as the medium shown in FIG. 1A except that the noble metal oxide layer 4 is made of PtOy (y = 2). Recording was performed on this medium under the same conditions as the medium shown in Fig. 1A except that the recording power level was changed to 10.5 mW, and the CNR was measured. As a result, CNR was not obtained at the playback power of lmW, but CNR of 40 dB or more was obtained at the playback power of 4 mW.
再生パワー lmWで再生した後の図 1 Aに示す媒体について、 断面の透過型電子 顕微鏡 (TEM) 写真を図 1 Bに示す。 また、 再生パワー 4mWで再生し、 次いで、 再生パワーを lmWとして再ぴ再生した後のこの媒体について、 断面の TEM写真 を図 1 Cに示す。 また、 再生パワー lmWで再生した後の図 14 Aに示す媒体につ いて、 断面の透過型電子顕微鏡 (TEM) 写真を図 14 Bに示す。 また、 再生パ ヮー 4mWで再生し、 次いで、 再生パワーを lmWとして再ぴ再生した後のこの媒体 について、 断面の TEM写真を図 14Cに示す。 これら各図に示す断面は、 記録 トラックとほぼ平行、 すなわち記録マーク列とほぼ平行である。  Fig. 1B shows a transmission electron microscope (TEM) photograph of a cross section of the medium shown in Fig. 1A after reproducing with the reproducing power lmW. In addition, FIG. 1C shows a TEM photograph of a cross section of the medium after reproduction at a reproduction power of 4 mW and then reproduction at a reproduction power of lmW. In addition, FIG. 14B shows a transmission electron microscope (TEM) photograph of a cross section of the medium shown in FIG. 14A after reproduction at a reproduction power of lmW. FIG. 14C shows a TEM photograph of a cross section of this medium after reproduction at a reproduction power of 4 mW and then reproduction reproduction at lmW. The cross section shown in each of these figures is substantially parallel to the recording track, that is, substantially parallel to the recording mark row.
図 1 Bから、 記録前に A g〇x層が存在していた領域に、 記録ビーム照射によ り空洞が形成されたこと、 この空洞の断面形状が周期的に変動しており、 その変 動周期が記録マークの配列ピッチの 40 Onmに対応していること、 が明瞭に見て 取れる。 したがって、 図 1 Bの空洞断面において、 凸部 （空洞の高さが相対的に 大きい領域） が記録パワーレベルのレーザービームを照射した領域 （記録マー ク） に対応し、 凹部 （空洞の高さが相対的に小さい領域） がバイアスパワーレべ ルのレーザービームを照射した領域 （スペース） に対応すると考えられる。 また、 空洞内には、 A g粒子 4 0がわずかに析出している。 また、 光吸収層 5は、 記録 前は非晶質であつたが、 記録後は、 記録したトラックの全域で結晶化していた。 図 1 Cから、 4 mWのパワーで再生した後には、 記録時に形成された空洞の輪郭 に変化は認められないが、 空洞中の A g粒子 4 0が顕著に増えていることがわか る。 すなわち、 再生レーザービーム照射により、 A g粒子の析出が生じたことが わかる。 なお、 空洞中において A g粒子 4 0は均一に分布しているわけではない 力 分布の不均一さによる再生信号の欠落は認められなかった。 From Fig. 1B, it was found that a cavity was formed by the recording beam irradiation in the area where the Ag x layer existed before recording, and that the cross-sectional shape of this cavity fluctuated periodically. It can be clearly seen that the dynamic period corresponds to the recording mark arrangement pitch of 40 Onm. Therefore, in the cavity cross section in Fig. 1B, the convex portion (the region where the cavity height is relatively large) corresponds to the region (recording mark) irradiated with the laser beam at the recording power level, and the concave portion (the cavity height). Is relatively small) is the bias power level. It is thought to correspond to the area (space) where the laser beam was irradiated. Ag particles 40 are slightly precipitated in the cavities. The light absorbing layer 5 was amorphous before recording, but crystallized after recording on the entire area of the recorded track. From FIG. 1C, it can be seen that there is no change in the contour of the cavity formed during recording after reproduction with a power of 4 mW, but the number of Ag particles 40 in the cavity has increased significantly. In other words, it can be seen that Ag particles were precipitated by the reproduction laser beam irradiation. The Ag particles 40 are not uniformly distributed in the cavity. No loss of the reproduced signal due to the non-uniform force distribution was observed.
一方、 図 1 4 Bおよび図 1 4じから、 貴金属酸化物層 4を P t Oyから構成し た場合にも、 貴金属酸ィ匕物層 4内に記録マークに対応する空洞が形成されること がわかる。 また、 この場合、 スペースに相当する領域には実質的に空洞が形成さ れず、 図 1 Bの A g Ox層に比べ、 記録マークに相当する空洞の外形がより明瞭 となっていることがわかる。 さらに、 図 1 4 Bおよぴ図 1 4じから、 P t Oy層 では、 記録時に空洞内に析出した P t粒子 4 1は、 4 mWの高パワーで再生しても、 形態、 粒径、 析出密度がほとんど変化しないことがわかる。 On the other hand, since Ji 1 4 B and FIG. 1 4, when the noble metal oxide layer 4 was formed from P t O y also cavity corresponding to the recording mark in the noble metal Sani匕物layer 4 is formed You can see that. In this case, no void is substantially formed in the area corresponding to the space, and the outer shape of the void corresponding to the recording mark is clearer than the AgO x layer in FIG.1B. Understand. Furthermore, since Ji FIG 1 4 B Oyopi Figure 1 4, the P t O y layer, P t particle 4 1 deposited in the cavity at the time of recording, even when played on high power 4 mW, form, grain It can be seen that the diameter and the precipitation density hardly change.
以上の結果から、 まず記録メカニズムの考察を行う。 A g Oxからなる貴金属 酸化物層 4では、 記録時 （記録パワーレベルのレーザービームを照射時） に A g Ox→A g + x / 2 02の分解と光吸収層 5の結晶化とが起こる。 記録時に発生し た酸素ガス （02) は、 貴金属酸化物層 4内で体積膨張を起こして貴金属酸化物 層 4を変形させるとともに第 2誘電体層 3 2と光吸収層 5とを押し上げる。 また、From the above results, the recording mechanism is first considered. Crystallization of A g O in the noble metal oxide layer 4 made of x, the recording time (the laser beam of the recording power level upon irradiation) A g O x → A g + x / 2 0 2 decomposition and the light absorbing layer 5 Happens. Oxygen gas generated during recording (0 2) pushes up the second dielectric layer 3 2 and the light absorbing layer 5 with undergo volume expansion in the noble metal oxide layer 4 to deform the noble metal oxide layer 4. Also,
P t Oyからなる貴金属酸ィ匕物層 4においても、 同様な分解が生じる。 その結果、 記録パワーレベルのレーザービームを照射した部位では、 第 2誘電体層 3 2が図 中の上方に突き出すように湾曲すると共に、 その周囲に比べ光吸収層 5の厚さが 薄くなり、 これによりこの部位は記録マークとして機能することになる。 形成さ れた空洞内には 02が封入されていると考えられる。 このメカニズムが働くため には、 貴金属酸化物が貴金属と o2とに分解すること、 分解によって発生した o2 が貴金属属酸化物層 4を変形させること、 すなわち第 2誘電体層 3 2と光吸収層 5も変形させること、 の 2つのプロセスが必要となる。 記録の際に、 典型的な相 変化記録材料からなる光吸収層 5が全面的に結晶化を起こしていることから、 こ の記録メカニズムは、 結晶質と非晶質との反射率の違いに基づいて記録マークを 検出する相変化型記録媒体における記録メ力ニズムとは異なる。 Even in the noble metal Sani匕物layer 4 made of P t O y, same decomposition occurs. As a result, at the portion irradiated with the laser beam at the recording power level, the second dielectric layer 32 is curved so as to protrude upward in the figure, and the thickness of the light absorbing layer 5 is smaller than the surrounding area, As a result, this portion functions as a recording mark. It is considered that O 2 is enclosed in the formed cavity. Because this mechanism works The, the noble metal oxide is decomposed into noble metal and o 2, that is o 2 generated by the decomposition deforming the noble metal belonging to the genus oxide layer 4, i.e., the second dielectric layer 3 2 and the light absorbing layer 5 deforms Two processes are required. During recording, the light absorbing layer 5 made of a typical phase-change recording material is entirely crystallized, so this recording mechanism is based on the difference in the reflectance between crystalline and amorphous. This is different from the recording mechanism in a phase change recording medium that detects a recording mark based on the recording mark.
次に、 再生メカニズムの考察を行う。 図 1 Cから、 超解像再生により A g粒子 4 0が多量に析出することが明らかとなった。 記録時に A g Oxから A g + x / 2 02への分解によって生成した A gは、 図 I Bに示されるように、 一部が凝集 して A g粒子 4 0となる。 図 1 Bからは確認できないが、 凝集しなかった A gは、 超微粒子の形で空洞の壁面に付着していると考えられる。 この状態において、 あ る程度以上のパワーをもつ再生レーザービームを照射すると、 A gの超微粒子が 凝集し、 T EMによって観察可能な程度の大きさの A g粒子が析出する。 そして、 この A g粒子が、 近接場光を散乱するプローブとなり、 前記 Jpn. J. Appl. Phys. Vo 1. 39 (2000) pp. 980- 981に記載された A gプローブと同様に機能して近接場光を伝 搬光に変換し、 超解像再生を可能にするものと考えられる。 Next, consider the regeneration mechanism. From FIG. 1C, it became clear that a large amount of Ag particles 40 were precipitated by super-resolution reproduction. At the time of recording was produced by the decomposition of the A g O x to A g + x / 2 0 2 A g , as shown in FIG IB, the A g particles 4 0 partially aggregated. Although not confirmed from Fig. 1B, Ag that did not aggregate is considered to be attached to the wall of the cavity in the form of ultrafine particles. In this state, when a reproducing laser beam having a certain level of power or more is irradiated, ultrafine Ag particles are aggregated, and Ag particles having a size observable by TEM are precipitated. The Ag particles serve as a probe that scatters near-field light, and function similarly to the Ag probe described in Jpn. J. Appl. Phys. Vo 1.39 (2000) pp. 980-981. It is considered that near-field light is converted to propagation light to enable super-resolution reproduction.
図 1 Bおよび図 1 Cでは、 マーク長おょぴスペース長がともに 2 0 O nmと短い ため、 マークでの O 2発生による貴金属酸化物 4の変形がスペースにも影響を及 ぼした結果、 スペースに相当する領域も空洞となっている。 し力 し、 より長いマ ーク長およびより長いスペース長をもつ記録マーク列を記録したところ、 スぺー スにおいて貴金属酸ィ匕物 4内に空洞は形成されず、 また、 マークにおいて空洞の 高さは一定であった。 In FIG. 1B and FIG. 1C, both the mark length and the space length are as short as 20 O nm, so that the deformation of the noble metal oxide 4 due to the generation of O 2 in the mark also affected the space, The area corresponding to the space is also hollow. When a record mark sequence having a longer mark length and a longer space length was recorded, no cavity was formed in the noble metal oxide 4 at the space, and the height of the cavity was increased at the mark. The length was constant.
本発明では、 再生時のレーザービーム照射によつて貴金属酸化物層 4の空洞内 にいつたん析出した貴金属粒子は、 再生後においても消失することはない。 した がって、 2回目以降の再生に際してさらに貴金属粒子を析出させる必要はない。 ただし、 4 mWのパワーで再生して図 1 Cに示される状態となった後、 再生パワー を l mWまで低下させたところ、 C N Rが得られなくなつたので、 2回目以降の再 生に際しても、 超解像再生が可能となる強度のレーザービームを照射する必要が ある。 In the present invention, the noble metal particles that have been deposited in the cavities of the noble metal oxide layer 4 by laser beam irradiation during reproduction do not disappear even after reproduction. Therefore, it is not necessary to precipitate further noble metal particles during the second and subsequent regenerations. However, after reproducing with the power of 4 mW to reach the state shown in Fig. 1C, when the reproducing power was reduced to 1 mW, the CNR could not be obtained. However, it is necessary to irradiate a laser beam with an intensity that enables super-resolution reproduction.
なお、 貴金属粒子の析出は、 再生レーザービームの照射によって行う必要はな く、 再生前に、 貴金属粒子析出のためにレーザービームを照射しておいてもよい。 また、 図 1 Bおよぴ図 1 Cに示す例では、 記録時に貴金属粒子がわずかに析出 しているが、 記録時における貴金属粒子の析出量はさらに多くてもよい。 たとえ ば、 図 1 4 Bおよぴ図 1 4 Cに示されるように、 記録時に貴金属粒子が多量に析 出して、 再生時など、 その後のレーザービーム照射時には貴金属粒子の析出密度 がほとんど変化しなくてもよい。 また、 記録時に析出した貴金属粒子の結晶構造 や粒径が、 再生時など、 その後のレーザービーム照射時に変化してもよい。  The precipitation of the noble metal particles does not need to be performed by irradiation with a reproduction laser beam, and may be performed before the reproduction by irradiating a laser beam for precipitation of the noble metal particles. In the examples shown in FIGS. 1B and 1C, noble metal particles are slightly precipitated during recording, but the amount of noble metal particles precipitated during recording may be larger. For example, as shown in Fig. 14B and Fig. 14C, a large amount of noble metal particles precipitate during recording, and the precipitation density of noble metal particles almost changes during subsequent laser beam irradiation, such as during reproduction. It is not necessary. Also, the crystal structure and particle size of the noble metal particles precipitated during recording may change during subsequent laser beam irradiation, such as during reproduction.
記録時および超解像再生時には、 貴金属酸化物層 4を透過したレーザービーム が光吸収層 5に照射されるように、 レーザービーム入射方向を設定することが好 ましい。 金属および Zまたは半金属からなる光吸収層 5を通してレーザービーム を貴金属酸ィヒ物層 4に照射する場合、 光吸収層 5による反射および吸収を考慮し て、 レーザービームのパワーを高くする必要があり、 光吸収層 5が破損するおそ れがある。 また、 光吸収層 5が相変化材料から形成される場合、 貴金属酸化物層 4を透過させずに光吸収層 5に直接レーザービームを照射すると、 貴金属酸化物 層 4に記録マークが形成されずに光吸収層 5に非晶質または結晶質からなる記録 マークが形成されることがある。 その場合、 本発明が特徴とする記録 Z再生メカ 二ズムが実現しなくなる。  It is preferable to set the laser beam incident direction so that the laser beam transmitted through the noble metal oxide layer 4 is irradiated on the light absorbing layer 5 during recording and super-resolution reproduction. When irradiating the laser beam to the noble metal oxide layer 4 through the light absorption layer 5 made of metal and Z or semimetal, it is necessary to increase the power of the laser beam in consideration of the reflection and absorption by the light absorption layer 5. Yes, the light absorbing layer 5 may be damaged. When the light absorbing layer 5 is formed of a phase-change material and a laser beam is directly applied to the light absorbing layer 5 without passing through the noble metal oxide layer 4, no recording mark is formed on the noble metal oxide layer 4. In some cases, an amorphous or crystalline recording mark is formed on the light absorbing layer 5. In such a case, the recording / reproducing mechanism characteristic of the present invention cannot be realized.
なお、 本発明は、 媒体が光吸収層 5を有しない場合も包含する。 その場合、 記 録時および再生時のレ、ずれにおいても、 レーザービームは媒体のどちらの面から 入射させてもよい。 ところで、 特許第 3157019号公報および特許第 3071243号公報に は、 酸化銀からなる記録層を有し、 記録ビーム照射により酸化銀が A gと 02と に分解されて記録層中に空隙が形成される光記録媒体が記載されている。 これら の光記録媒体は、 記録時に酸ィヒ銀層中に空隙が形成される点で本発明が適用され る媒体と類似する。 しかし、 これらの公報では、 解像限界付近の寸法をもつ微小 な記録マークの再生について全く着目しておらず、 また、 これらの公報の実施例 では、 再生レーザービームとして波長 78 Onm、 パワー 0. 5 mWのものを用いて いるが、 この程度の再生パワーでは A g粒子を析出させることはできないため、 超解像再生は不可能である。 Note that the present invention includes a case where the medium does not have the light absorbing layer 5. In such a case, the laser beam may be incident from any surface of the medium, even during recording and playback, and at the time of deviation. Meanwhile, Japanese Patent No. 3157019 discloses and Patent No. 3071243 publication, has a recording layer consisting of silver oxide, voids in the recording layer of silver oxide by recording beam irradiation is decomposed into A g and 0 2 is formed An optical recording medium to be used is described. These optical recording media are similar to the media to which the present invention is applied in that voids are formed in the silver oxide layer during recording. However, these publications do not pay any attention to the reproduction of minute recording marks having dimensions near the resolution limit, and in the embodiments of these publications, the reproduction laser beam has a wavelength of 78 Onm and a power of 0. Although a 5 mW power is used, Ag particles cannot be precipitated with this level of reproducing power, so super-resolution reproduction is impossible.
光記録媒体に情報を記録する際には、 EFM等のデータ変調方式によって変調 された信号に基づいてレーザービーム強度を変調して媒体に照射し、 様々な長さ の記録マークを含む記録マーク列を記録トラックに形成する。 本発明は、 解像限 界である 0. 25 λ/ΝΑより小さい記録マークを再生する際に高 CNRが得ら れるという優れた効果を示す。 また、 解像限界より大きいが解像限界に近い微小 な記録マークを再生する際にも、 CNR向上効果が実現する。 CNR向上効果が 大きいのは、 マーク長が 0. 37ぇ/ΝΑ未満、 特に 0. 28え /Ν Α以下であ る記録マークを再生するときである。 したがって本発明は、 このような寸法の記 録マークを含む記録マーク列を形成する場合に有効である。  When information is recorded on an optical recording medium, the laser beam intensity is modulated based on a signal modulated by a data modulation method such as EFM and the medium is irradiated, and a recording mark array including recording marks of various lengths Is formed on the recording track. The present invention has an excellent effect that a high CNR can be obtained when reproducing a recording mark smaller than the resolution limit of 0.25 λ / ΝΑ. Also, the CNR improvement effect is realized when reproducing minute recording marks that are larger than the resolution limit but close to the resolution limit. The CNR improvement effect is large when playing back recorded marks whose mark length is less than 0.37 ぇ / ΝΑ, especially 0.28 特 に / え or less. Therefore, the present invention is effective when forming a recording mark row including recording marks of such dimensions.
なお、 マーク長が著しく短いと、 本発明によっても高 CNRを得ることが困難 となるため、 本発明は、 マーク長が 0. 05 λΖΝΑ以上、 特に 0. 09λΖΝ If the mark length is extremely short, it is difficult to obtain a high CNR according to the present invention. Therefore, in the present invention, the mark length is 0.05 λΖΝΑ or more, particularly 0.09λΖΝ.
Α以上の記録マークを含む記録マーク列の再生に適用することが好ましい。 本発明では、 記録時に、 貴金属酸化物を分解して貴金属酸ィヒ物層中に空洞を形 成し、 再生前または少なくとも初回の再生時に、 貴金属粒子を不可逆的に析出さ せる必要がある。 記録パワーおよび/または再生パワーが低すぎると、 このよう な記録 Z再生メカニズムが十分に働かなくなり、 高 CNRが得られない。 一方、 記録パワーおよび Zまたは再生パワーが高すぎると、 媒体の耐久性に影響を与え、 媒体が損傷することがある。 したがって、 記録パワーおょぴ再生パワーには、 最 適値が存在する。 Α It is preferable to apply the present invention to reproduction of a record mark row including the above-mentioned record marks. In the present invention, at the time of recording, it is necessary to decompose the noble metal oxide to form cavities in the noble metal oxide layer, and to irreversibly precipitate the noble metal particles before reproduction or at least during the first reproduction. If the recording power and / or reproducing power is too low, such a recording / reproducing mechanism will not work sufficiently, and a high CNR cannot be obtained. on the other hand, If the recording power and Z or reproduction power are too high, the durability of the media will be affected and the media may be damaged. Therefore, there is an optimum value for the recording power and the reproduction power.
ただし、 短波長のレーザービームを開口数の大きい光学系で照射すると、 ビー ムスポット内のエネルギー密度が高くなるので、 波長おょぴ開口数が異なる条件 では、 レーザービームのパヮ一が同じであってもそれが記録時および再生時に貴 金属酸化物層に与える影響は異なる。 また、 貴金属酸化物層や光吸収層など、 媒 体を構成する各層の構成材料や厚さが異なる場合、 レーザービームのパヮ一が同 じであってもそれが記録時および再生時に貴金属酸ィヒ物層に与える影響は異なる。 したがって、 本発明において記録パワーおょぴ再生パワーは、 高 C N Rが得ら れるように実験的に決定すればよい。 なお、 本発明では、 好ましくは 2 5 dB以上、 より好ましくは 4 O dB以上の C N Rが得られることが望ましい。  However, when a short-wavelength laser beam is irradiated by an optical system with a large numerical aperture, the energy density in the beam spot increases, so that under the condition that the wavelength and numerical aperture are different, the laser beam has the same power. However, the effect on the noble metal oxide layer during recording and during reproduction is different. Also, if the constituent materials and thicknesses of the layers constituting the medium, such as the noble metal oxide layer and the light absorbing layer, are different, even if the laser beam has the same pattern, it is noble metal oxide during recording and reproduction. The effect on the moss layer is different. Therefore, in the present invention, the recording power and the reproducing power may be experimentally determined so as to obtain a high CNR. In the present invention, it is desirable to obtain a CNR of preferably 25 dB or more, more preferably 40 dB or more.
以下、 本発明の記録 Z再生方法が適用される媒体について、 詳細に説明する。 図 2に示す媒体構造  Hereinafter, a medium to which the recording and Z reproducing method of the present invention is applied will be described in detail. Media structure shown in Fig. 2
本発明の光記録媒体の構成例を図 2に示す。 この媒体は、 基板 2上に、 第 1誘 電体層 3 1、 貴金属酸化物層 4、 第 2誘電体層 3 2、 光吸収層 5および第 3誘電 体層 3 3をこの順で有する。 貴金属酸化物層 4  FIG. 2 shows a configuration example of the optical recording medium of the present invention. This medium has a first dielectric layer 31, a noble metal oxide layer 4, a second dielectric layer 32, a light absorbing layer 5 and a third dielectric layer 33 on a substrate 2 in this order. Noble metal oxide layer 4
記録前の媒体において、 貴金属酸化物層 4は貴金属酸化物を含有し、 好ましく は、 実質的に貴金属酸ィ匕物だけから構成される。  In the medium before recording, the noble metal oxide layer 4 contains a noble metal oxide, and is preferably substantially composed of only a noble metal oxide.
貴金属酸化物層には、 2種以上の貴金属酸ィヒ物が含有されていてもよい。 その 場合、 貴金属酸化物層は単層構造であってもよく、 それぞれ少なくとも 1種の貴 金属酸化物を含有する層を複数積層した積層構造であってもよい。 ただし、 貴金 属酸ィヒ物層に 2種以上の貴金属酸ィヒ物が含有される場合、 記録時に 2種以上の貴 金属酸ィ匕物のすべてが同時には分解しないことがあり、 また、 再生時に 2種以上 の貴金属のすべてが同時には凝集しないことがあり、 これらにより記録/再生特 性が悪影響をうけることがある。 したがって、 貴金属酸化物層には貴金属酸化物 が 1種だけ含有されることが好ましい。 The noble metal oxide layer may contain two or more kinds of noble metal oxides. In that case, the noble metal oxide layer may have a single-layer structure or a stacked structure in which a plurality of layers each containing at least one type of noble metal oxide are stacked. However, precious money When two or more noble metal oxides are contained in the generic acid layer, not all of the two or more noble metal oxides may be simultaneously decomposed at the time of recording, and at the time of reproduction. All of the precious metals or species may not aggregate at the same time, which may adversely affect recording / reproducing characteristics. Therefore, it is preferable that the noble metal oxide layer contains only one kind of noble metal oxide.
本発明で用いる貴金属の種類は特に限定されず、 前述した記録 Z再生メカニズ ムは、 どの貴金属を用いた場合でも機能するが、 酸化物の形成のしゃすさ、 酸ィ匕 物の安定性、 可視光による近接場光の発生効率の観点から、 白金、 銀おょぴパラ ジゥムの少なくとも 1種が好ましく、 銀おょぴ Zまたは白金がより好ましく、 よ り高い C N Rが得られ、 かつ再生耐久性が高くなることから、 特に白金が好まし 白金酸化物を用いる場合、 これを P t oyで表したとき、 微小な記録マークを 再生する際に高い C N Rを得るためには、 好ましくは The kind of the noble metal used in the present invention is not particularly limited, and the above-described recording / reproducing mechanism functions even when any noble metal is used. However, the formation of oxide, the stability of the oxide, the visible From the viewpoint of the efficiency of near-field light generation by light, at least one of platinum and silver oxide platinum is preferable, silver silver Z or platinum is more preferable, higher CNR is obtained, and reproduction durability is obtained. In particular, when platinum oxide is used, and this is represented by P to y , it is preferable to obtain a high CNR when reproducing a minute recording mark.
0 . 5≤y、 より好ましくは  0.5≤y, more preferably
1≤y  1≤y
とする。 ただし、 yが大きいと、 解像限界よりマーク長が大きい記録マークを再 生する際の C N Rが低くなつてしまうため、 様々な長さの記録マークを含む記録 マーク列を再生する際に高い出力を得るためには、 好ましくは And However, if y is large, the CNR at the time of playing a recording mark whose mark length is longer than the resolution limit will be low, so a high output will be obtained when playing back a recording mark sequence including recording marks of various lengths. In order to obtain
y≤4 , より好ましくは  y≤4, more preferably
y < 3  y <3
である。 また、 P t Oyの組成は、 再生耐久性にも関わる。 解像限界より小さい 記録マークの再生耐久性を十分なものとするためには、 すなわち繰り返し再生に よる C N R低下を抑えるためには、 好ましくは It is. The composition of P t O y is involved in the reproduction durability. In order to make the reproduction durability of a recording mark smaller than the resolution limit sufficient, that is, to suppress the CNR decrease due to repeated reproduction,
i≤y  i≤y
とし、 解像限界よりマーク長が大きい記録マークの再生耐久性を十分なものとす るためには、 好ましくは And that the reproduction durability of recorded marks with mark lengths longer than the resolution limit is sufficient. In order to
2<y  2 <y
とする。 And
銀酸化物を用いる場合、 これを A gOxで表したとき、 微小な記録マークを再 生する際に高い CNRを得るためには、 好ましくは When silver oxide is used, when expressed as AgO x , in order to obtain a high CNR when reproducing minute recording marks, it is preferable to use silver oxide.
0. 5≤x≤l. 5、 より好ましくは  0.5≤x≤l.5, more preferably
0. 5≤ X≤ 1  0.5 ≤ X≤ 1
である。 Xが小さすぎると高 CNRが得られにくく、 Xが大きすぎると AgOx が不安定となるため、 保存耐久性および再生耐久性が低くなりやすレ、。 It is. If X is too small, it is difficult to obtain a high CNR, and if X is too large, AgO x becomes unstable, so that storage durability and reproduction durability tend to be low.
パラジウム酸化物を用いる場合、 これを P dOzで表したとき、 微小な記録マ ークを再生する際に高い CNRを得るためには、 好ましくは When using a palladium oxide, when it was expressed in P dO z, in order to obtain a high CNR when reproducing a small recording mark is preferably
1. 0≤ z≤ 1. 5  1.0 ≤ z ≤ 1.5
である。 zが小さすぎると高 CNRが得られにくい。 一方、 成膜プロセスの都合 上、 Zが 1. 5を超えるパラジウム酸ィ匕物膜を形成することは困難である。 It is. If z is too small, it is difficult to obtain a high CNR. On the other hand, it is difficult to form a palladium oxide film with Z exceeding 1.5 due to the film forming process.
なお、 貴金属酸化物層 4の組成は、 たとえば蛍光 X線分析により測定すること ができる。  The composition of the noble metal oxide layer 4 can be measured by, for example, X-ray fluorescence analysis.
貴金属酸ィ匕物層 4の厚さは、 好ましくは 1〜3 Onm、 より好ましくは 2〜20 nmである。 貴金属酸化物層 4が薄すぎると、 連続膜とすることが困難となり、 安 定した記録/再生特性が得られにくい。 一方、 貴金属酸化物層 4が厚すぎると、 高い CNRが得られなくなる。  The thickness of the noble metal oxide layer 4 is preferably 1 to 3 Onm, more preferably 2 to 20 nm. If the noble metal oxide layer 4 is too thin, it is difficult to form a continuous film, and it is difficult to obtain stable recording / reproducing characteristics. On the other hand, if the noble metal oxide layer 4 is too thick, a high CNR cannot be obtained.
なお、 図 2から光吸収層 5を取り去った構造 （図 5に示す構造） も、 本発明に 包含される。 この構造の媒体では、 レーザービーム照射の際に貴金属酸化物層 4 が十分には昇温しにくく、 その結果、 十分に高い CNRが得られにくい。 そのた め、 光吸収層 5を設けない構造においては、 貴金属酸化物層 4を厚くして光吸収 率を高めることが好ましい。 この構造における貴金属酸化物層 4の好ましい厚さ は、 2 0〜1 0 O nmである。 この場合に貴金属酸ィ匕物層 4が厚すぎると、 貴金属 酸化物層 4が不安定となって再生耐久性が低くなりやすい。 Note that a structure in which the light absorbing layer 5 is removed from FIG. 2 (the structure shown in FIG. 5) is also included in the present invention. In the medium having this structure, the temperature of the noble metal oxide layer 4 is not sufficiently raised during laser beam irradiation, and as a result, it is difficult to obtain a sufficiently high CNR. Therefore, in a structure in which the light absorption layer 5 is not provided, it is preferable that the noble metal oxide layer 4 is thickened to increase the light absorption. Preferred thickness of noble metal oxide layer 4 in this structure Is 20 to 10 O nm. In this case, if the noble metal oxide layer 4 is too thick, the noble metal oxide layer 4 becomes unstable and the reproduction durability tends to decrease.
貴金属酸化物層 4の形成方法は特に限定されず、 スパッタリング、 蒸着などの 物理的気相堆積法 （P VD) や、 化学的気相堆積法 （C VD) を用いることがで きる。 これらのうちでは、 貴金属ターゲットを用い、 酸素を反応ガスとして用い る反応性スパッタリング法が好ましい。 光吸収層 5  The method for forming the noble metal oxide layer 4 is not particularly limited, and a physical vapor deposition (PVD) such as sputtering or vapor deposition, or a chemical vapor deposition (CVD) can be used. Among them, a reactive sputtering method using a noble metal target and using oxygen as a reaction gas is preferable. Light absorbing layer 5
光吸収層 5は、 再生時にレーザービームを吸収して昇温することにより、 隣り 合う貴金属酸化物層 4を昇温して貴金属析出を促進する。 貴金属酸化物層 4は、 記録 Z再生用のレーザービームに対する透明性が高いため加熱されにくいので、 光吸収層を設けないと十分に高い C N Rを得ることが困難となる。  The light absorbing layer 5 absorbs the laser beam during reproduction and raises the temperature, thereby raising the temperature of the adjacent noble metal oxide layer 4 to promote the noble metal deposition. Since the noble metal oxide layer 4 has high transparency to the laser beam for recording / reproducing Z and is hard to be heated, it is difficult to obtain a sufficiently high CNR unless a light absorbing layer is provided.
光吸収層 5は、 レーザービーム照射により十分に昇温するように構成する。 そ のためには、 光吸収層 5を、 吸収係数の高いものとしたり、 熱伝導率の低いもの としたりすればよい。 また、 本発明では前述したメカニズムで空洞形成により記 録マークを形成する必要があるため、 空洞形成を妨げないように、 光吸収層 5を 変形しやすいものとすることが好ましい。  The light absorption layer 5 is configured to sufficiently raise the temperature by laser beam irradiation. For this purpose, the light absorption layer 5 may have a high absorption coefficient or a low thermal conductivity. Further, in the present invention, since the recording mark needs to be formed by forming a cavity by the above-described mechanism, it is preferable that the light absorbing layer 5 be easily deformed so as not to hinder the formation of the cavity.
光吸収層 5の構成材料としては、 金属および半金属から選択された 1種または 2種以上の元素を含む金属または合金 （金属間化合物が包含される） を主成分と するものが好ましく、 光吸収層 5に要求される上記特性を実現しやすいことから、 少なくとも S bおよび/または T eを含有する合金が好ましい。  The constituent material of the light absorbing layer 5 is preferably a material mainly composed of a metal or an alloy (including an intermetallic compound) containing one or more elements selected from metals and metalloids. An alloy containing at least Sb and / or Te is preferable because the above properties required for the absorption layer 5 can be easily realized.
S bおよび/または T eを含有する合金の糸且成としては、  As the material of the alloy containing Sb and / or Te,
式 I ( S b aT e i—a) ト bMb Formula I (S b a T ei — a ) to b M b
で表されるものが好ましい。 上記式 Iにおいて、 元素 Mは S bおよび T eをそれ ぞれ除く元素を表し、 aおよび bは原子比を表し、 好ましくは 0≤ a≤ 1 Is preferably represented by In the above formula I, the element M represents an element excluding S b and Te, respectively, and a and b represent an atomic ratio, preferably 0≤ a≤ 1
0≤b≤0 . 2 5  0≤b≤0. 2 5
である。 元素 Mの含有量を表す bが大きすぎると、 光吸収層に要求される前記特 性が不十分となりやすい。 元素 Mは特に限定されないが、 たとえば I n、 A g、 A u、 B i、 S e、 A l、 P、 G e、 H、 S i、 C、 V、 W、 T a、 Z n、 T iヽ S n、 P b、 P dおよび希土類元素 （S c、 Yおよびランタノイド） から選択さ れる少なくとも 1種が好ましい。 It is. If the value of b representing the content of the element M is too large, the characteristics required for the light absorbing layer tend to be insufficient. The element M is not particularly limited, but for example, In, Ag, Au, Bi, Se, Al, P, Ge, H, Si, C, V, W, Ta, Zn, T i ヽ At least one selected from Sn, Pb, Pd and rare earth elements (Sc, Y and lanthanoids) is preferred.
. なお、 上記式 Iで表される組成をもつ合金には、 相変化記録材料として知られ ている合金が含まれる。 相変化記録材料は、 結晶質時の反射率と非晶質時の反射 率との相違を利用して、 非晶質または結晶質からなる記録マークを読み出す媒体 の記録材料として使われる合金である。 ただし、 本発明における光吸収層 5は、 結晶質時の反射率と非晶質時の反射率との相違を利用する相変化型記録層として は使用されない。  Note that alloys having the composition represented by the above formula I include alloys known as phase change recording materials. A phase change recording material is an alloy used as a recording material for a medium for reading a recording mark made of an amorphous or crystalline material by utilizing a difference between a reflectance in a crystalline state and a reflectance in an amorphous state. . However, the light absorbing layer 5 in the present invention is not used as a phase change type recording layer utilizing the difference between the reflectance in a crystalline state and the reflectance in an amorphous state.
光吸収層 5が相変化記録材料からなり、 かつ、 非晶質である場合において、 貴 金属酸化物層 4に短い記録マークだけを記録する際には、 記録時に光吸収層 5面 内への熱拡散により、 光吸収層 5は記録トラック方向に連続的に結晶化される、 すなわちマーク間 （スペース） においても光吸収層 5は結晶化されるため、 再生 時に問題は生じない。 し力 し、 貴金属酸ィヒ物層 4に長いスペースを形成する際に は、 スペース中央付近において光吸収層 5が非晶質のまま残ることがある。 非晶 質のまま残った領域は、 再生時に結晶化することがあり、 この結晶化により再生 信号に乱れが生じることがある。  When the light absorbing layer 5 is made of a phase change recording material and is amorphous and only a short recording mark is to be recorded on the noble metal oxide layer 4, the light absorbing layer 5 may be placed on the surface of the light absorbing layer 5 during recording. Due to the thermal diffusion, the light absorption layer 5 is continuously crystallized in the recording track direction, that is, the light absorption layer 5 is crystallized even between the marks (spaces), so that no problem occurs during reproduction. However, when a long space is formed in the noble metal oxide layer 4, the light absorbing layer 5 may remain amorphous near the center of the space. The region that remains amorphous may be crystallized during reproduction, and this crystallization may cause disturbance in the reproduced signal.
光吸収層 5が非晶質である場合に生じるこのような再生信号の乱れを防ぐため には、 貴金属酸化物層 4に記録する前に、 光吸収層 5の全域を結晶化しておくこ とが好ましい。 この結晶化は、 相変化型媒体における記録層の全面結晶化 （初期 ィ匕） と同様に、 レーザービーム照射によって行うことができる。 ただし、 光吸収 層 5の結晶化処理に際しては、 貴金属酸化物層 4において貴金属酸化物の分解が 生じないように処理条件を設定する必要がある。 In order to prevent such a disturbance of the reproduced signal that occurs when the light absorption layer 5 is amorphous, the entire area of the light absorption layer 5 must be crystallized before recording on the noble metal oxide layer 4. Is preferred. This crystallization can be performed by laser beam irradiation as in the case of the entire crystallization of the recording layer in the phase change medium (initial shading). However, light absorption In the crystallization treatment of the layer 5, it is necessary to set processing conditions so that the noble metal oxide does not decompose in the noble metal oxide layer 4.
光吸収層 5の厚さは、 薄すぎると十分な光吸収率を確保することが困難となり、 厚すぎると記録時に変型しにくくなるため、 好ましくは 2〜2 0 0 nm、 より好ま しくは 1 0〜： 1 0 O nmとする。  If the thickness of the light absorbing layer 5 is too small, it is difficult to secure a sufficient light absorption rate, and if the thickness is too large, it is difficult to deform during recording, so it is preferably 2 to 200 nm, more preferably 1 to 200 nm. 0 to: 10 O nm.
光吸収層 5の形成方法は特に限定されず、 前記した P V D法や C V D法を用い ることができる。  The method for forming the light absorbing layer 5 is not particularly limited, and the above-described PVD method or CVD method can be used.
L、 3 2、 3 3 L, 3 2, 3 3
第 1誘電体層 3 1は、 記録 Z再生時に貴金属酸化物層 4から伝わる熱を面内方 向に逃がすことにより基板 2を保護するために、 また、 媒体の反射率を制御する ために設けられる。 第 2誘電体層 3 2は、 C N R向上おょぴ貴金属酸化物層 4の 保護のために設けられる。 第 3誘電体層 3 3は、 光吸収層 5を保護するために設 けられる。 第 2誘電体層 3 2は、 記録時に貴金属酸ィヒ物層 4での空洞形成に伴つ て変形する必要があるため、 変形しやすい構成とすることが好ましい。  The first dielectric layer 31 is provided to protect the substrate 2 by dissipating heat transmitted from the noble metal oxide layer 4 in the in-plane direction during recording Z reproduction, and to control the reflectance of the medium. Can be The second dielectric layer 32 is provided for protecting the CNR and protecting the noble metal oxide layer 4. The third dielectric layer 33 is provided to protect the light absorbing layer 5. Since the second dielectric layer 32 needs to be deformed along with the formation of a cavity in the noble metal oxide layer 4 during recording, it is preferable that the second dielectric layer 32 be configured to be easily deformed.
各誘電体層の厚さは、 その機能が十分に発揮されるように適宜決定すればよ 1ヽ 力 通常、 第 1誘電体層 3 1は 1 0〜3 0 O nm、 第 2誘電体層 3 2は 5 nm以上 1 0 0 nm未満、 好ましくは 1 0〜 6 0 nm、 第 3誘電体層 3 3は 1 0〜 2 0 0 nmであ ることが好ましい。 第 2誘電体層 3 2が厚すぎても薄すぎても、 超解像再生時の C N Rが低くなつてしまう。  The thickness of each dielectric layer may be appropriately determined so that its function is sufficiently exhibited. 1 output Normally, the first dielectric layer 31 has a thickness of 10 to 30 O nm, and the second dielectric layer has a thickness of 10 to 30 O nm. 32 is 5 nm or more and less than 100 nm, preferably 10 to 60 nm, and the third dielectric layer 33 is preferably 10 to 200 nm. If the second dielectric layer 32 is too thick or too thin, the CNR during super-resolution reproduction will be low.
各誘電体層に用いる誘電体としては、 例えば、 S i、 G e、 Z n、 Aし 希土 類元素などから選択される少なくとも 1種の金属成分または半金属成分を含む各 種化合物が好ましい。 化合物としては、 酸化物、 窒化物または硫化物が好ましく、 これらの化合物の 2種以上を含有する混合物を用いることもできる。 ただし、 第 2誘電体層 3 2を変形しやすくするためには、 窒化ケィ素をはじめとする窒化物 は好ましくない。 As the dielectric used for each dielectric layer, for example, various compounds containing at least one metal component or metalloid component selected from Si, Ge, Zn, A, and rare earth elements are preferable. . The compound is preferably an oxide, a nitride or a sulfide, and a mixture containing two or more of these compounds can also be used. However, in order to make the second dielectric layer 32 easily deformable, nitride such as silicon nitride must be used. Is not preferred.
なお、 第 3誘電体層 3 3上に、 媒体の保護を目的として樹脂製の保護層を設け てもよい。 また、 光吸収層 5が相変化材料から構成される場合には第 3誘電体層 3 3を設けることが好ましいが、 第 3誘電体層 3 3を設けることは必須ではなく、 光吸収層 5に接して樹脂保護層を形成してもよい。  Note that a resin protective layer may be provided on the third dielectric layer 33 for the purpose of protecting the medium. When the light absorbing layer 5 is made of a phase change material, it is preferable to provide the third dielectric layer 33. However, it is not essential to provide the third dielectric layer 33, and the light absorbing layer 5 is not necessary. , A resin protective layer may be formed.
これらの誘電体層の形成方法は特に限定されず、 前記した P V D法や C V D法 を用いることができる。 基板 2  The method for forming these dielectric layers is not particularly limited, and the above-described PVD method or CVD method can be used. Board 2
基板 2は、 媒体の剛性を維持するために設けられる。 基板 2の厚さは、 通常、 0 . 2〜1 . 2腿、 好ましくは 0 . 4〜1 . 2醒とすればよい。 基板 2には、 通 常、 トラッキングのためのグループ （案内溝） を設ける。  The substrate 2 is provided to maintain the rigidity of the medium. The thickness of the substrate 2 may be generally from 0.2 to 1.2 thighs, preferably from 0.4 to 1.2. The substrate 2 is usually provided with a group (guide groove) for tracking.
なお、 本発明では、 第 1誘電体層 3 1から第 3誘電体層 3 3までの各層を、 図 2に示す積層順とは逆に基板上に積層してもよい。  Note that, in the present invention, the layers from the first dielectric layer 31 to the third dielectric layer 33 may be laminated on the substrate in the reverse order of the lamination shown in FIG.
基板 2側からレーザービームを媒体に入射させる場合には、 透光性材料から基 板 2を構成する。 基板 2の構成材料は、 必要とされる剛性や透明性などに応じ、 樹脂、 ガラス、 金属、 セラミック等の各種材料から選択すればよい。 図 3に示す媒体構造  When a laser beam is incident on the medium from the substrate 2 side, the substrate 2 is made of a translucent material. The constituent material of the substrate 2 may be selected from various materials such as resin, glass, metal, and ceramic according to the required rigidity and transparency. Media structure shown in Fig. 3
図 3に示す媒体は、 図 2に示す媒体の第 3誘電体層 3 3上に、 反射層 6を設け た構造である。 反射層 6を設ける場合、 記録 Z再生用のレーザービームは、 図中 の下側から媒体に入射させる。  The medium shown in FIG. 3 has a structure in which a reflective layer 6 is provided on the third dielectric layer 33 of the medium shown in FIG. When the reflective layer 6 is provided, the laser beam for recording / reproducing Z is made incident on the medium from the lower side in the figure.
反射層 6を設けることにより、 解像限界より大きなマーク長をもつ記録マ一ク の再生出力を向上させることができる。 反射層 6を設けない構造では、 光吸収層 5と第 3誘電体層 3 3との界面を通過した光はすべて媒体の外側へ透過する。 そ のため、 近接場光を使わずに伝搬光の反射を検出することにより読み出される記 録マーク、 すなわち、 超解像再生ではなく通常再生が可能な寸法の記録マークで は、 CNRが大きくならない。 これに対し、 反射層 6を設ければ、 第 3誘電体層 33と反射層 6との界面で反射した光とその他の界面で反射した光との干渉効果 が利用できるようになるので、 伝搬光だけで再生することのできる大きさの記録 マークの CNRが増大するものと考えられる。 By providing the reflective layer 6, the reproduction output of a recording mark having a mark length larger than the resolution limit can be improved. In the structure without the reflection layer 6, all light passing through the interface between the light absorption layer 5 and the third dielectric layer 33 is transmitted to the outside of the medium. So Therefore, the CNR does not increase for recording marks that are read out by detecting the reflection of propagating light without using near-field light, that is, recording marks that are sized to allow normal reproduction instead of super-resolution reproduction. On the other hand, if the reflection layer 6 is provided, the interference effect between the light reflected at the interface between the third dielectric layer 33 and the reflection layer 6 and the light reflected at the other interface can be used, so that the propagation It is thought that the CNR of a recording mark of a size that can be reproduced only by light increases.
ただし、 反射層 6を厚くすると、 反射層 6で反射して光ピックアップに戻る伝 搬光の強度が高くなる結果、 貴金属酸化物層 4において近接場光から変換されて 光ピックアツプに戻る伝搬光の強度が相対的に低くなるため、 超解像再生の対象 となる微小な記録マークの CNRが低くなつてしまう。 したがって、 反射層 6の 厚さは、 大きな記録マークおよび微小な記録マークの双方において十分な C N R が得られるように設定することが好ましい。 具体的には、 反射層 6構成材料に応 じて実験的に決定すればよいが、 通常、 l〜100nm、 特に 2〜15nmとするこ とが好ましい。  However, when the thickness of the reflection layer 6 is increased, the intensity of the transmitted light that is reflected by the reflection layer 6 and returns to the optical pickup increases, and as a result, the propagation light that is converted from the near-field light and returned to the optical pickup in the noble metal oxide layer 4 Since the intensity is relatively low, the CNR of the minute recording mark that is the subject of super-resolution reproduction will be low. Therefore, it is preferable to set the thickness of the reflective layer 6 so that sufficient CNR can be obtained for both large recording marks and minute recording marks. Specifically, it may be determined experimentally according to the material constituting the reflective layer 6, but it is usually preferably 1 to 100 nm, particularly preferably 2 to 15 nm.
反射層 6は、 Al、 Au、 Ag、 P t、 Cu、 N i、 C r、 T i、 S i等の金 属または半金属の単体や、 金属または半金属を 2種以上含有する合金から構成す ればよい。  The reflective layer 6 is made of a single metal or semimetal such as Al, Au, Ag, Pt, Cu, Ni, Cr, Ti, Si, or an alloy containing two or more metals or semimetals. It may be configured.
反射層 6の形成方法は特に限定されず、 前記した P VD法や C VD法を用いる ことができる。 図 4に示す媒体構造  The method for forming the reflective layer 6 is not particularly limited, and the above-described PVD method or CVD method can be used. Media structure shown in Fig. 4
図 4に示す媒体は、 図 2に示す媒体の第 1誘電体層 31と貴金属酸化物層 4と の間に、 析出促進層 7を設けた構造である。  The medium shown in FIG. 4 has a structure in which the precipitation promoting layer 7 is provided between the first dielectric layer 31 and the noble metal oxide layer 4 of the medium shown in FIG.
貴金属酸化物層 4に接触する層の材料に依存して、 再生時の貴金属粒子の析出 温度が変化する。 一方、 再生耐久性の観点からは、 超解像再生のための再生パヮ 一は低いほど好ましい。 そのため、 貴金属酸化物層 4に接して、 貴金属粒子の析 出温度を低下させる機能をもつ層を設けることが好ましい。 この層は、 媒体のト 一タルな光学的設計や熱的パランスを損なわない程度の厚さとすることが好まし い。 析出促進層 7は、 このように再生感度を向上させる機能をもつ層であり、 こ れを設けることにより、 設けない場合に比べてより低い再生パワーで同等の C N Rが得られるようになる。 Depending on the material of the layer in contact with the noble metal oxide layer 4, the precipitation temperature of the noble metal particles during regeneration changes. On the other hand, from the viewpoint of reproduction durability, a reproduction power for super-resolution reproduction is required. The lower the one, the better. Therefore, it is preferable to provide a layer having a function of lowering the precipitation temperature of the noble metal particles in contact with the noble metal oxide layer 4. This layer is preferably thick enough to not impair the overall optical design and thermal balance of the media. The precipitation accelerating layer 7 is a layer having a function of improving the reproduction sensitivity as described above. By providing this layer, the same CNR can be obtained with a lower reproduction power as compared with the case where no such layer is provided.
析出促進層 7は、 たとえば窒化ケィ素から構成し、 厚さは 2〜2 O nmとするこ とが好ましい。  The precipitation promoting layer 7 is preferably made of, for example, silicon nitride, and preferably has a thickness of 2 to 2 O nm.
析出促進層 7の形成方法は特に限定されず、 前記した P V D法や C V D法を用 いることができる。  The method for forming the precipitation promoting layer 7 is not particularly limited, and the above-described PVD method or CVD method can be used.
なお、 図 3に示す反射層 6と図 4に示す析出促進層 7とを、 ともに設けてもよ レ、。 図 5に示す媒体構造  The reflection layer 6 shown in FIG. 3 and the precipitation promoting layer 7 shown in FIG. 4 may be provided together. Media structure shown in Fig. 5
図 5に示す媒体は、 図 2に示す媒体から光吸収層 5およぴ第 3誘電体層 3 3を 取り去った構造である。  The medium shown in FIG. 5 has a structure in which the light absorbing layer 5 and the third dielectric layer 33 are removed from the medium shown in FIG.
この構造の媒体でも、 超解像再生は可能であり、 また、 再生耐久性は良好であ る。 ただし、 高い C N Rを得ることは困難である。 実施例  Super-resolution reproduction is possible with this type of medium, and reproduction durability is good. However, it is difficult to obtain a high CNR. Example
以下の実施例において、 光ディスクサンプルの評価には、 開口数 ΝΑ== 0 · 6 0の光学系から波長 λ = 6 3 5 nmのレーザービームを射出する低分解能ピックァ ップ （解像限界ピッチ 5 3 O nm、 解像限界マーク長 2 6 5 nm) と、 開口数 NA = 0 . 6 5の光学系から波長 λ = 4 0 5 nmのレ一ザ一ビームを射出する高分解能ピ ックアップ （解像限界ピッチ 3 1 2 nm、 解像限界マーク長 1 5 6 nm) とが対向し て搭載してある光ディスク評価装置 （パルステック社製 DDU1000) を用い た。 記録および再生の際の線速度は 6 m/sとした。 In the following examples, an optical disk sample was evaluated by using a low-resolution pickup (a resolution limit pitch of 5) that emits a laser beam having a wavelength of λ = 635 nm from an optical system having a numerical aperture ΝΑ == 0.60. 3 O nm, resolution limit mark length 2 65 nm) and a high-resolution pick-up (solution) that emits a laser beam with a wavelength λ = 405 nm from an optical system with a numerical aperture NA = 0.65. (Primary image pitch 3 12 nm, resolution limit mark length 1 56 nm) An optical disk evaluation device (DDU1000 manufactured by Pulstec) was installed. The linear velocity during recording and playback was 6 m / s.
この評価装置では、 低分解能ピックァップから出射されたレーザービームは、 基板側から貴金属酸化物層 4に入射し、 高分解能ピックァップから出射されたレ 一ザ一ビームは、 基板とは反対側から貴金属酸ィ匕物層 4に入射する。 そのため、 この評価装置では、 貴金属酸化物層 4に記録された記録マーク列を、 分解能の異 なる 2つのピックアツプでそれぞれ再生することが可能である。 たとえば、 配列 ピッチ 400nm (マーク長 200nm) の記録マーク列の再生は、 λ = 635ηιη、 NA=0. 60の低分解能ピックァップでは超解像再生に相当し、 え = 405 nm、 NA=0. 65の高分解能ピックアップでは通常再生に相当する。  In this evaluation device, the laser beam emitted from the low-resolution pickup enters the noble metal oxide layer 4 from the substrate side, and the laser beam emitted from the high-resolution pickup is emitted from the opposite side of the substrate from the noble metal oxide. The incident light enters the dangling object layer 4. Therefore, in this evaluation device, it is possible to reproduce the record mark sequence recorded on the noble metal oxide layer 4 with two pick-ups having different resolutions. For example, reproduction of a recorded mark array with an array pitch of 400 nm (mark length 200 nm) is equivalent to super-resolution reproduction in a low-resolution pickup with λ = 635ηιη and NA = 0.60, e = 405 nm, NA = 0.65. The high-resolution pickup corresponds to normal reproduction.
したがって、 両方のピックアップにおいて CNRが得られないことは、 読み取 り可能な記録マークが形成されなかったことを意味する。 また、 繰り返し再生に 伴って C N Rが低下することは、 繰り返し再生に伴つて記録マークが消滅したこ とを意味する。 また、 高分解能ピックアップでは通常再生が可能で、 低分解能ピ ックァップでは超解像再生が必要な寸法の記録マークを再生する際に、 低分解能 ピックァップを用いた超解像条件でのみ C N Rが得られな!/、ことは、 記録マーク は存在しているが超解像再生メカニズムが働いていないことを意味する。  Therefore, the fact that no CNR was obtained with both pickups means that no readable recording mark was formed. Further, a decrease in CNR with repeated playback means that the recording mark has disappeared with repeated playback. In addition, normal reproduction is possible with a high-resolution pickup, and a CNR can be obtained only under super-resolution conditions using a low-resolution pickup when reproducing recording marks of dimensions that require super-resolution reproduction with a low-resolution pickup. That means that the recording mark is present but the super-resolution playback mechanism is not working.
なお、 以下の実施例では、 特に断りのない限り、 記録は低分解能ピックアップ により行った。 実施例 1一 1 (図 2の構造：貴金属酸化物 A g Ox) In the following examples, recording was performed using a low-resolution pickup unless otherwise specified. Example 11 (Structure of FIG. 2: Noble metal oxide A g O x )
図 2に示すように、 基板 2 Z第 1誘電体層 31Z貴金属酸化物層 4/第 2誘電 体層 32 /光吸収層 5 Z第 3誘電体層 33からなる積層構造を有する光ディスク サンプルを形成した。 各層の組成および厚さは、 ポリカーボネート基板 (0. 6 麵） /Z n S— S i〇2 ( 1 3 Onm) /A g〇x ( 18 nm) /Z n S - S i 02 (4 Onra) /A g- I n-S b-T e ( 60 nm) / Z n S - S i O2 ( 100 nm) と した。 かっこ内は厚さである。 Z n S— S i〇2層は、 モル比で表した組成が (Zn S) 85 (S i〇2) 15であるターゲットを A r雰囲気中でスパッタリングす ることにより形成した。 AgOx層は、 ArZ〇2= 1 Osccm : 1 Osccmの流量比 の混合ガス雰囲気中で A gターゲットをスパッタリングすることにより形成した。 形成された A gOxにおける Xは 1であった。 Ag— I n— S b—T e層は、 A g6.。I n4.5S b6。.8T e28.7 (モル0 /o) ターゲットを A r雰囲気中でスパッタリン グすることにより形成した。 As shown in FIG. 2, an optical disk sample having a laminated structure composed of a substrate 2 Z first dielectric layer 31 Z noble metal oxide layer 4 / second dielectric layer 32 / light absorbing layer 5 Z third dielectric layer 33 is formed. did. The composition and thickness of each layer, a polycarbonate substrate (0.6 noodles) / Z n S- S I_〇 2 (1 3 Onm) / A G_〇 x (18 nm) / Z n S - S i 0 2 (4 Onra) / A g- I nS bT e (60 nm) / Z n S - was S i O 2 (100 nm) . The thickness in parentheses is the thickness. The ZnS—Si 2 layer was formed by sputtering a target having a composition represented by a molar ratio of (Zn S) 85 (Si 2 ) 15 in an Ar atmosphere. The AgO x layer was formed by sputtering an Ag target in a mixed gas atmosphere having a flow rate ratio of ArZ〇 2 = 1 Osccm: 1 Osccm. X in the formed AgO x was 1. Ag- I n- S b-T e layer, A g 6 .. I n 4. 5 S b 6 . . 8 T e 28. 7 (molar 0 / o) targets were formed by sputtering-ring in A r atmosphere.
サンプル形成後、 サンプルを線速度 6 m/sで回転させながら、 記録対象トラッ クに対し、 低分解能ピックアップにより 1. 2mWのパワーのレーザービームを 3 秒間連続照射することにより、 光吸収層 5を結晶化させた。 なお、 特に断りのな い限り、 以下の実施例においてもこの実施例と同様にして、 記録/再生特性を評 価する前に光吸収層 5を結晶化させた。  After forming the sample, the light absorption layer 5 was irradiated by continuously irradiating the recording target track with a 1.2 mW laser beam for 3 seconds with a low-resolution pickup while rotating the sample at a linear velocity of 6 m / s. Crystallized. Unless otherwise specified, in the following examples, the light absorption layer 5 was crystallized before evaluating the recording / reproducing characteristics in the same manner as in this example.
このサンプルに、 記録パワー 1 OmWで、 配列ピッチ 200 nm~ 1. 6 ιη (マ ーク長 100〜80 Onm) の記録マーク列をそれぞれ記録した後、 低分解能ピッ クアップを用いて再生パワー P r = lmWまたは 4mWで再生し、 CNRを測定した。 結果を図 6に示す。  After recording a record mark array with an array pitch of 200 nm to 1.6 ιη (mark length 100 to 80 Onm) at a recording power of 1 OmW and a recording power of 1 = Playback at lmW or 4mW and CNR measured. Fig. 6 shows the results.
図 6から、 マーク長 40 Onm未満 (0. 37え ZN A未満） の記録マークから なる記録マーク列を再生する際に、 再生パワーを 4mWとすることにより特異的に CNRが増大していることがわかる。 特に、 マーク長 20 Onmの記録マークから なるマーク列では、 4 ldBという高い CNRが得られている。  From Fig. 6, it can be seen that when reproducing a recording mark sequence consisting of recording marks with a mark length of less than 40 Onm (less than 0.37 E ZA), the CNR is specifically increased by setting the reproduction power to 4 mW. I understand. In particular, a CNR of as high as 4 ldB has been obtained for a mark train consisting of recording marks with a mark length of 20 Onm.
なお、 光吸収層 5の組成 （モル比） を G e2S b2T e5または （S b。.7Te。,3) 0. 95G e0.05とした場合でも、 ほぼ同様な結果が得られた。 The composition of the light absorbing layer 5 (molar ratio) G e 2 S b 2 T e 5 or (S b .. 7 Te., 3) 0. 95 even when the G e 0. 05, almost the same The result was obtained.
前記した図 1 Bおよび図 1 Cにそれぞれ示す TEM写真は、 この実施例と同条 件で記録/再生を行った実験におけるサンプル断而写真である。 ただし、 その実 験に際しては、 記録前に光吸収層 5は結晶化させなかった。 比較例 1 (図 2の構造：光吸収層 5への相変化型記録） The TEM photographs shown in FIG. 1B and FIG. 1C described above are sample metamorphic photographs in an experiment in which recording / reproduction was performed under the same conditions as in this example. However, In the experiment, the light absorbing layer 5 was not crystallized before recording. Comparative Example 1 (Structure in FIG. 2: Phase-change recording on the light absorbing layer 5)
実施例 1一 1と同様にしてサンプルを作製した。 ただし、 光吸収層 5は結晶化 させなかった。  Example 11 A sample was prepared in the same manner as in Example 1. However, the light absorbing layer 5 was not crystallized.
このサンプルに対し、 高分解能ピックアップを用いて第 3誘電体層 3 3側から レーザービームを入射させて、 配列ピッチ 4 0 0 nm (マーク長 2 0 0 nm) の記録 マーク列を記録パワー 6 mWで記録し、 高分解能ピックアップを用いて 0 . 7 mWの パワーで再生したところ、 4 4 dBの C N Rが得られた。  A laser beam is applied to this sample from the third dielectric layer 33 side using a high-resolution pickup, and a recording mark array with an arrangement pitch of 400 nm (mark length of 200 nm) is recorded at a recording power of 6 mW. And reproduced with a power of 0.7 mW using a high-resolution pickup, a CNR of 44 dB was obtained.
次に、 低分解能ピックアップを用いて 4 mWのパワーで連続的に再生したところ、 初期には 2 2 dBの C N Rが得られたが、 数秒以内に信号が完全に消滅した。 その 後、 高分解能ピックアップを用いて 0 . 7 mWのパワーで再生したところ、 C N R は得られなかった。  Next, continuous playback with 4 mW of power using a low-resolution pickup resulted in an initial 22 dB CNR, but the signal completely disappeared within seconds. After that, using a high-resolution pickup and reproducing at a power of 0.7 mW, CNR was not obtained.
4 mWのパヮ一のレーザービームを連続的に照射したときに記録マーク列が消滅 したことから、 この比較例では、 非晶質の光吸収層 5に結晶質記録マークが形成 される相変化型記録がなされていると考えられ、 この記録マーク列に対し、 低分 解能ピックアツプで貴金属酸化物層 4に A g粒子を析出させながら超解像再生を 行ったものと考えられる。 すなわち、 この比較例における記録/再生方法は、 相 変化型記録を行っている点で、 前記 Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 980- 981に 記載されている方法に近い。 この比較例 1と上記実施例 1—1との比較から明ら かなように、 相変化型記録を行った場合には、 得られる C N Rが低く力つ再生耐 久性も劣る。 実施例 1一 2 (図 2の構造：貴金属酸化物 P t〇y) In this comparative example, a phase change type in which a crystalline recording mark was formed on the amorphous light absorbing layer 5 was observed because the recording mark array disappeared when continuously irradiated with a 4 mW laser beam. It is considered that recording was performed, and it is probable that super-resolution reproduction was performed on the recorded mark row while depositing Ag particles on the noble metal oxide layer 4 with a low-resolution pickup. That is, the recording / reproducing method in this comparative example is similar to the method described in Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 980-981 in that phase change recording is performed. near. As is clear from the comparison between Comparative Example 1 and Example 1-1, when phase-change recording is performed, the obtained CNR is low and the reproduction durability is inferior. Example 11 (Structure of FIG. 2: noble metal oxide P t〇 y )
実施例 1一 1における貴金属酸化物層 4を P t Ov ( 4讓） に替えたサンプル を作製した。 P tOy層は、 P tターゲットを A r /O2= 5sccm/5sccmの流量 比の混合ガス雰囲気中でスパッタリングすることにより形成した。 P t Oyにお ける yは 2であった。 Samples for changing the noble metal oxide layer 4 in Example 1 one 1 to P t O v (4 Yuzuru) Was prepared. P tO y layer was formed by sputtering P t target in a mixed gas atmosphere flow ratio A r / O 2 = 5sccm / 5sccm. Y in PtOy was 2.
このサンプルについて、 記録パワー 14mWで、 配列ピッチ 16 Οηπ！〜 1. 6 μ m (マーク長 80〜80 Onm) のマーク列をそれぞれ記録し、 低分解能ピックァ ップを用いて再生パワー P r = lmWまたは 4mWで再生した。 結果を図 7に示す。 図 7において、 再生パワー P r = lmWのとき、 マーク長が 40 Onm (0. 37 λ/ΝΑ) より小さくなると CNRが急激に減少し、 解像限界より小さい 200 nmのマークでは CNRが得られていない。 これに対し、 再生パワー P r =4mWで は、 超解像再生が必要な微小な記録マークであっても、 十分に高い CNRが得ら れている。 具体的には、 マーク長 1 5 Onm以上の全ての記録マークで、 40dB以 上の CNRが得られている。  For this sample, at a recording power of 14 mW, an array pitch of 16 Οηπ! Mark rows of ~ 1.6 μm (mark length 80-80 Onm) were recorded, and were reproduced using a low-resolution pickup with a reproduction power Pr = lmW or 4 mW. Fig. 7 shows the results. In Fig. 7, when the read power Pr = lmW, the CNR sharply decreases when the mark length is less than 40 Onm (0.37 λ / ΝΑ), and the CNR is obtained for a 200 nm mark smaller than the resolution limit. Not. On the other hand, with the reproduction power Pr = 4 mW, a sufficiently high CNR can be obtained even for minute recording marks that require super-resolution reproduction. More specifically, all record marks with a mark length of 15 Onm or more have a CNR of 40 dB or more.
AgOxを用いた図 6と P t Oyを用いた図 7とを比較すると、 超解像再生が可 能な再生パワー P r =4mWのとき、 全てのマーク長において図 7のほうが C NR が高いことがわかる。 したがって、 貴金属酸化物層 4を構成する貴金属酸化物と しては白金酸ィヒ物が望ましい。 Comparing Figure 7 with Figure 6 and P t O y using AgO x, when super-resolution reproduction is possible reproduction power P r = 4 mW, is better in Figure 7 in all mark lengths C NR Is high. Therefore, the noble metal oxide constituting the noble metal oxide layer 4 is preferably a platinum oxide.
前記した図 14 A、 図 14Bおよび図 14Cにそれぞれ示す TEM写真は、 こ の実施例と同条件で記録/再生を行つた実験におけるサンプル断面写真である。 ただし、 その実験に際しては、 記録前に光吸収層 5は結晶化させなかった。 実施例 1一 3 (図 2の構造：貴金属酸化物 P d Oz) The TEM photographs shown in FIG. 14A, FIG. 14B, and FIG. 14C are sample cross-sectional photographs in an experiment in which recording / reproduction was performed under the same conditions as in this example. However, in the experiment, the light absorbing layer 5 was not crystallized before recording. Example 11 (Structure of FIG. 2: Noble metal oxide P d O z )
実施例 1—1における貴金属酸化物層 4を P dOz (4nm) に替えたサンプル を作製した。 P dOjiは、 P dターゲットを A r /〇2= 5sccm/5sccmの流量 比の混合ガス雰囲気中でスパッタリングすることにより形成した。 P d〇zにお ける zは 1. 10であった。 このサンプルについて、 高分解能ピックアップと同一の光学系を用いて、 基板 側から記録パワー 1 lmWで、 配列ピッチ 100〜80 Onm (マーク長 50〜40 Onm) のマーク列をそれぞれ記録し、 高分解能ピックアップを用いて、 基板側か ら再生パワー P r = lmWまたは 4mWで再生した。 結果を図 15に示す。 The noble metal oxide layer 4 in Example 1-1 to prepare a sample was changed to P dO z (4nm). P DOji was formed by sputtering P d target in a mixed gas atmosphere flow ratio A r / 〇 2 = 5sccm / 5sccm. Z in P d〇 z was 1.10. For this sample, using the same optical system as the high-resolution pickup, a mark power with a recording power of 1 lmW and an array pitch of 100 to 80 Onm (mark length 50 to 40 Onm) was recorded from the substrate side, and the high-resolution pickup was recorded. It was used to play the substrate side or playback from the power P r = LMW or 4 mW. The results are shown in FIG.
図 15において、 再生パワー P r = lmWのとき、 マーク長が 200 nmより小さ くなると C N Rが急激に減少し、 解像限界より小さい 150 rnnのマークでは C N Rがほとんど得られていない。 これに対し、 再生パワー P r =4mWでは、 超解像 再生が必要な微小な記録マークであっても、 十分に高い CNRが得られている。 具体的には、 マーク長 10 Onm以上の全ての記録マークで、 35dB以上の CNR が得られている。  In FIG. 15, when the read power P r = lmW, the CNR decreases sharply when the mark length is smaller than 200 nm, and almost no CNR is obtained for a mark of 150 rnn smaller than the resolution limit. On the other hand, with the reproduction power P r = 4 mW, a sufficiently high CNR is obtained even for minute recording marks that require super-resolution reproduction. Specifically, all recorded marks with a mark length of 10 Onm or more have a CNR of 35 dB or more.
なお、 同一のサンプルについて低分解能ピックアップを用いて記録再生を行つ たところ、 記録パワー 12mW、 再生パワー P r =4mWの条件で、 解像限界よりも 小さい 20 Onmのマークで 42dBの CNRが得られた。 実施例 1—4 (図 2の構造： P t Oy層の酸素含有量による比較） When the same sample was recorded and reproduced using a low-resolution pickup, a recording power of 12 mW and a reproduction power of Pr = 4 mW resulted in a CNR of 42 dB at a mark of 20 Onm smaller than the resolution limit. Was done. Example 1-4 (Structure of Fig. 2: Comparison by oxygen content of PtOy layer)
実施例 1—2の構造において、 P t Oy層形成に際し流量比 A r /〇2を制御し て、 yの相異なる P t Oy層を有する複数のサンプルを作製した。 各サンプルに おける yの値と流量 （単位： sccm) の比とは、 In the structure of Example 1-2, by controlling the flow rate ratio A r / 〇 2 upon P t O y layer is formed to prepare a plurality of samples having different P t O y layer of y. The ratio between the value of y and the flow rate (unit: sccm) in each sample is
y = 0 ： Ατ /θ2= 10/0、 y = 0: Ατ / θ 2 = 10/0,
y = 0. 75 ： A r /〇2= 7. 5/2. 5、 y = 0.75: A r / 〇 2 = 7.5 / 2.5 ,
y = 2 ： A r /θ2= 5. 0/5. 0、 y = 2: Ar / θ 2 = 5.0 / 5. 0,
y = 3 ： A r /θ2=2. 5/7. 5 y = 3: A r / θ 2 = 2.5 / 7.5
である。 これらのサンプルに対し、 各々の最適記録パワーで、 配列ピッチ 160 nn！〜 1. 6 μηι (マーク長 80〜80 Onm) の記録マーク列をそれぞれ記録し、 低分解能ピックアップを用いて 4 の再生パワーで再生した。 結果を図 8に示す。 また、 図 9およぴ図 10に、 配列ピッチ 400nm (マーク長 200nm) の記録 マーク列および配列ピッチ 1. 6 μ m (マーク長 800 nni) の記録マーク列を繰 り返し再生したときの CNRの変化をそれぞれ示す。 図 9およぴ図 10から、 様々な長さの記録マークにおいて良好な再生耐久性を得るためには、 yを大きく したほうがよいことがわかる。 実施例 1—5 (図 2の構造： P d Oz層の酸素含有量による比較） It is. For these samples, at the optimum recording power, the array pitch is 160 nn! A series of recording marks of ~ 1.6 μηι (mark length 80-80 Onm) were recorded and reproduced with a reproduction power of 4 using a low-resolution pickup. Fig. 8 shows the results. Figures 9 and 10 show the CNR when a recorded mark array with an array pitch of 400 nm (mark length 200 nm) and a recorded mark array with an array pitch of 1.6 μm (mark length 800 nni) were repeatedly reproduced. The change of each is shown. From FIGS. 9 and 10, it can be seen that it is better to increase y in order to obtain good reproduction durability with recording marks of various lengths. Example 1-5 (Structure of Fig. 2: Comparison by oxygen content of PdOz layer)
実施例 1一 3の構造において、 P d Ojl形成に際し流量比 A r /〇2を制御し て、 zの相異なる P dOjiを有する複数のサンプルを作製した。 各サンプルに おける zの値と流量 （単位： sccm) の比とは、 In the structure of Example 1 one 3, by controlling the flow rate ratio A r / 〇 2 upon P d Ojl formed, plural samples were prepared having different P DOji of z. The ratio between the value of z and the flow rate (unit: sccm) for each sample is
y = 0. 82 : Ar/02=8. 5/1. 5、 y = 0.82: Ar / 0 2 = 8.5 / 1. 5,
y = 1. 10 ： Ar/02=5. 0/5. 0、 y = 1. 10:.. Ar / 0 2 = 5 0/5 0,
y = 1. 12 ： Ar/02= 1. 0/9. 0 y = 1. 12:. Ar / 0 2 = 1. 0/9 0
である。 これらのサンプルに対し、 高分解能ピックアップを用いて、 各々の最適 記録パワーで、 配列ピッチ 200〜60 Onm (マーク長 100〜30 Onm) の記 録マーク列をそれぞれ記録し、 高分解能ピックアップを用いて 4 mWの再生パヮ一 で再生した。 結果を図 16に示す。 It is. These samples were recorded using a high-resolution pickup with a recording pitch of 200 to 60 Onm (mark length of 100 to 30 Onm) at each optimum recording power. Playback was performed at a playback power of 4 mW. The results are shown in FIG.
図 16から、 角军像限界よりも小さいマークで高い CNRを得るためには、 1. 0≤zとすることが好ましいことがわかる。 また、 この結果からは、 zの上限は 特に限定されないが、 成膜時に雰囲気ガス中における酸素の比率を著しく高くし ても、 1. 5く zとなるようなパラジウム酸化物層を得ることは困難であること がわかった。 実施例 1—6 (図 2の構造： P t〇y層と A g Ox層との比較） From FIG. 16, it can be seen that in order to obtain a high CNR with a mark smaller than the angular image limit, it is preferable to set 1.0 ≦ z. From this result, although the upper limit of z is not particularly limited, it is not possible to obtain a palladium oxide layer having a z value of 1.5 even if the ratio of oxygen in the atmosphere gas is significantly increased during film formation. It turned out to be difficult. Example 1-6 (the structure of Figure 2: Comparison with P T_〇 y layer and A g O x layer)
実施例 1 _ 1で作製した Ag OJ1 (x=l) を有するサンプルと、 P tOy層 (y = 3) の厚さを 8 nmとしたほかは実施例 1一 4と同様にして作製したサンプ ルとについて、 配列ピッチ 400nm (マーク長 200nm) の記録マーク列および 配列ピッチ 1. 6 μ m (マーク長 800 nm) の記録マーク列を、 低分解能ピック アップを用いて 4 mWの再生出力で繰り返し再生したときの CNRの変化を調べた。 結果を図 1 1に示す。 And samples with Ag OJ1 (x = l) prepared in Example 1 _ 1, P tO y layer A recording mark array having an arrangement pitch of 400 nm (mark length 200 nm) and an arrangement pitch of 1.6 μm were obtained for the sample prepared in the same manner as in Example 14 except that the thickness of (y = 3) was 8 nm. The change in CNR was examined when a recorded mark array of m (mark length 800 nm) was repeatedly reproduced with a reproduction output of 4 mW using a low-resolution pickup. The results are shown in FIG.
図 1 1力 ら、 貴金属酸化物層 4として P t Oy層を用いたサンプルにおいて、 再生耐久性が大幅に向上することがわかる。 P t Oy層では、 再生時に析出した 貴金属粒子の形状および大きさ力 高パヮ一で繰り返し再生を行っても変動しに くく安定であると考えられる。 実施例 1—7 (図 2の構造： P t Oy層の膜厚による比較） It can be seen from FIG. 11 that the reproduction durability of the sample using the PtOy layer as the noble metal oxide layer 4 is greatly improved. The P t O y layer is considered to be repeatedly performed playback shape and size force high Pawa one noble metal particles precipitated at the time of reproduction is Kuku stable vary. Example 1-7 (Structure of Fig. 2: Comparison by PtOy layer thickness)
P t Oyからなる貴金属酸化物層 4を y = 3となる条件で形成し、 その膜厚を 4〜3 Onmの範囲内で変更したほかは実施例 1一 4と同様にしてサンプルを作製 した。 これらのサンプルに、 それぞれの最適条件で配列ピッチ 40 Onm (マーク 長 20 Onm) の記録マーク列を記録し、 低分解能ピックアップを用いて 4mWの再 生パワーで再生し、 CNRを測定した。 各サンプルの P t Oy層の厚さと CNR との関係は、 「厚さ ： CNR」 の形で表して、 The P t O y made of a noble metal oxide layer 4 was formed under conditions such that the y = 3, a sample prepared in the same manner as the film thickness except that changed within the range of 4 to 3 onm the Example 1 one 4 did. In each of these samples, a recording mark array with an array pitch of 40 Onm (mark length of 20 Onm) was recorded under optimum conditions, and the CNR was measured by reproducing with a 4 mW reproduction power using a low-resolution pickup. Relationship between the thickness and the CNR of P t O y layer of each sample, "thickness: CNR" expressed in the form of,
4nm： 44 dB、  4nm: 44 dB,
8nm： 41 dB、  8nm: 41 dB,
12nm： 30 dB、  12nm: 30 dB,
16nm： 29 dB、  16nm: 29 dB,
18nm： 28 dB、  18nm: 28 dB,
3 Onm : 27dB  3 Onm: 27dB
であった。 実施例 1—8 (図 2の構造： P dOjlの膜厚による比較） Met. Example 1-8 (Structure in Fig. 2: Comparison by PdOjl film thickness)
P dOzからなる貴金属酸化物層 4を z = 1. 10となる条件で形成し、 その 膜厚を 2〜： 15 nmの範囲内で変更したほかは実施例 1— 5と同様にしてサンプル を作製した。 これらのサンプルに、 高分解能ピックアップを用いて、 それぞれの 最適条件で配列ピッチ 30 Onm (マーク長 15 Onm) の記録マーク列を記録し、 高分解能ピックァップを用いて 4 mWの再生パヮ一で再生し、 C N Rを測定した。 各サンプルの P (102層の厚さと CNRとの関係は、 「厚さ ： CNR」 の形で表 して、 The noble metal oxide layer 4 made of P dO z formed under the condition that the z = 1. 10, 2~ its thickness: addition to vary within the range of 15 nm in the same manner as in Example 15 sample Was prepared. Using a high-resolution pickup, a recording mark array with an array pitch of 30 Onm (mark length 15 Onm) was recorded on each of these samples under the optimum conditions, and reproduced using a high-resolution pickup at a playback power of 4 mW. The CNR was measured. The relationship between the P (10 2 layer thickness and CNR of each sample is expressed as “thickness: CNR”.
2 nm： 26 dB、  2 nm: 26 dB,
4 nm： 35 dB、  4 nm: 35 dB,
1 Onm： 32 dB、  1 Onm: 32 dB,
15nm： 26dB  15nm: 26dB
であった。 実施例 1一 9 (図 2の構造：光吸収層 5の構成材料による比較） Met. Example 11-9 (structure of FIG. 2: comparison with constituent materials of light absorbing layer 5)
光吸収層 5を S i、 A uまたは Wで構成したほかは実施例 1 _ 1と同様にして 作製したサンプルに、 記録パワー 9 mWで配列ピッチ 40 Onm (マーク長 20 On m) の記録マーク列を記録し、 低分解能ピックアップを用いて 4mWの再生パワー で再生したところ、 光吸収層 5構成材料と C N Rとの関係は、  A recording mark having a recording power of 9 mW and an arrangement pitch of 40 Onm (mark length of 20 On m) was formed on a sample prepared in the same manner as in Example 1-1 except that the light absorption layer 5 was composed of Si, Au or W. When a row was recorded and read with a read power of 4 mW using a low-resolution pickup, the relationship between the light absorbing layer 5 constituent material and CNR was:
S i ： 19dB、  S i: 19dB,
A u ： 20 dB、  A u: 20 dB,
W ： 24dB  W: 24dB
であった。 Met.
この結果は、 光吸収層 5構成材料として A u、 S iまたは Wを用いると、 相変 化材料を用いる場合に比べ超解像記録特性が悪くなることを示している。 貴金属 酸化物層 4を構成する A g Oxそれ自体は吸収係数が小さいため、 この実施例に おける条件では昇温が不十分となり、 記録時に分解しない。 したがって、 適切な 光吸収層の存在が必要となる。 光吸収層 5を A uまたは S iで構成した場合に十 分な特性が得られなかったのは、 A uの場合は熱伝導率が高いので A g Ox層に 熱が伝わりにくかったためであると考えられ、 S iの場合は S iの吸収係数が小 さいため光吸収層として十分に機能しなかったためであると考えられる。 Wを用 いた場合は、 光を吸収して昇温する層としては機能するが、 Wは硬い材料である ため、 記録時の貴金属酸化物層 4における空洞形成を阻害したものと考えられる。 実施例 1一 1 0 (図 2の構造：第 2誘電体層 3 2の構成材料による比較） This result indicates that when Au, Si, or W is used as the constituent material of the light absorbing layer 5, the super-resolution recording characteristics are worse than when the phase change material is used. Precious metal Since the A g O x itself constituting the oxide layer 4 is small absorption coefficient, the heating becomes insufficient in definitive conditions of this example, not decomposed at the time of recording. Therefore, an appropriate light-absorbing layer must be present. In order sufficient characteristics the light absorbing layer 5 when configured in A u or S i is not been of the obtained, which in the case of A u was hard heat is transferred to the A g O x layer because of the high thermal conductivity This is considered to be because Si had a small absorption coefficient and did not function sufficiently as a light absorbing layer. When W is used, it functions as a layer that absorbs light and raises the temperature. However, W is a hard material, and it is considered that the formation of cavities in the noble metal oxide layer 4 during recording was inhibited. Example 11 (Comparing the structure of FIG. 2 with the constituent material of the second dielectric layer 32)
第 2誘電体層 3 2を窒化ケィ素から構成したほかは実施例 1一 1と同様にして 作製したサンプルについて、 記録パワー 1 4 mWで、 配列ピッチ 4 0 0 nm (マーク 長 2 0 0 nm) の記録マーク列を記録し、 低分解能ピックアップを用いて 4 mWの再 生パヮ一で再生したところ、 C N Rは得られなかった。  A sample fabricated in the same manner as in Example 11 except that the second dielectric layer 32 was made of silicon nitride was used. At a recording power of 14 mW, an array pitch of 400 nm (mark length of 200 nm) ) Was recorded and played back at a playback power of 4 mW using a low-resolution pickup, but no CNR was obtained.
また、 上記記録マーク列を高分解能ピックアップを用いて 0 . 7 mWの再生パヮ 一を再生したところ、 C N Rは得られなかった。 すなわち、 通常再生も不可能で あつ 7こ。  Further, when the above recording mark array was reproduced at a reproduction power of 0.7 mW using a high-resolution pickup, CNR was not obtained. In other words, normal playback is not possible.
このように通常再生も不可能であることから、 第 2誘電体層 3 2を窒化ケィ素 から構成すると、 読み取り可能な記録マークを形成できないことがわかる。 窒化 ケィ素は、 実施例 1— 1で用いた Z n S— S i〇2に比べてはるかに硬い材料で あるため、 A g Oxの分解により生成した〇2が、 記録マークとして機能する空洞 を貴金属酸化物層 4中に形成できなかったためと考えられる。 実施例 1一 1 1 (図 2の構造：第 2誘電体層 3 2の膜厚による比較） Since normal reproduction is impossible as described above, it is understood that a readable recording mark cannot be formed when the second dielectric layer 32 is made of silicon nitride. Nitride Keimoto are the material much harder than the Z n S- S I_〇 2 used in Example 1-1, A g O 〇 2 produced by the decomposition of x function as a recording mark It is considered that a cavity could not be formed in the noble metal oxide layer 4. Example 1 1 1 1 (Structure of FIG. 2: Comparison based on film thickness of second dielectric layer 32)
第 2誘電体層 3 2の膜厚を 1 0 O nmとしたほかは実施例 1— 1と同様にしてサ ンプルを作製した。 このサンプルに記録パワー 1 lmWで、 配列ピッチ 4 0 Onm (マーク長 2 0 0nm) の記録マーク列を記録し、 低分解能ピックアップを用いて 4 mWの再生パワーで再生したところ、 CNRは得られなかった。 The same procedure as in Example 1-1 was carried out except that the thickness of the second dielectric layer 32 was 10 O nm. A sample was prepared. When a recording mark array with an array pitch of 40 Onm (mark length of 200 nm) was recorded on this sample at a recording power of 1 lmW, and reproduced with a reproduction power of 4 mW using a low-resolution pickup, no CNR was obtained. Was.
また、 上記記録マーク列を記録した直後および低分解能ピックアップにより 4 mWで再生した後のそれぞれにおいて、 高分解能ピックアップを用いて 0. 7mWの 再生パワーで再生したところ、 いずれの場合も 4 OdB以上のCNRが得られた。 実施例 2— 1 (図 3の構造：反射層 6の効果）  Immediately after recording the above record mark sequence and after reproducing at 4 mW with a low-resolution pickup, reproduction was performed with a reproduction power of 0.7 mW using a high-resolution pickup. CNR was obtained. Example 2-1 (Structure of FIG. 3: Effect of the reflective layer 6)
実施例 1一 1で作製したサンプルの第 3誘電体層 3 3の上に、 反射層 6として 厚さ 1 Onmの Ag層または A 1層を形成することにより、 図 3に示す構造のサン プルを得た。 A g層おょぴ A 1層は、 それぞれ A gターゲットおよび A 1ターゲ ットを A r雰囲気中でスパッタリングすることにより形成した。  Example 1 An Ag layer or A1 layer having a thickness of 1 Onm was formed as a reflective layer 6 on the third dielectric layer 33 of the sample prepared in Example 1 to obtain a sample having the structure shown in FIG. I got The Ag layer and the A1 layer were formed by sputtering an Ag target and an A1 target in an Ar atmosphere, respectively.
これらのサンプルについて、 記録パワー 1 OmWで、 配列ピッチ 4 0 Onn！〜 1. 6 μιη (マーク長 2 0 0〜8 0 Onm) の記録マーク列をそれぞれ形成し、 低分解 能ピックアップを用いて 4mWの再生パワーで再生した結果を、 図 1 2に示す。 な お、 図 1 2には、 反射層 6を設けないサンプルの結果も示してある。  For these samples, the recording power is 1 OmW and the array pitch is 40 Onn! Figure 12 shows the results of forming recording mark arrays of ~ 1.6 μιη (mark length 200 to 80 Onm) and reproducing them with a reproduction power of 4 mW using a low-resolution pickup. FIG. 12 also shows the result of a sample in which the reflective layer 6 was not provided.
図 1 2から、 反射層 6を設けることにより、 解像限界よりも大きな記録マーク の C NRが増大することがわかる。 実施例 2— 2 (図 3の構造：反射層 6の膜厚による比較）  From FIG. 12, it can be seen that the provision of the reflective layer 6 increases the CNR of a recording mark larger than the resolution limit. Example 2-2 (structure in FIG. 3: comparison based on thickness of reflective layer 6)
反射層 6を図 1 3に示す厚さとしたほかは実施例 2— 1と同様にしてサンプル を作製した。 これらのサンプルについて、 それぞれの最適記録パワーで配列ピッ チ 4 0 Onm (マーク長 20 Onm) の記録マーク列を記録し、 低分解能ピックアツ プを用いて 4mWの再生パワーで再生した結果を、 図 1 3に示す。  A sample was produced in the same manner as in Example 2-1 except that the reflective layer 6 had the thickness shown in FIG. For these samples, a record mark array with an array pitch of 40 Onm (mark length 20 Onm) was recorded at the optimum recording power for each, and the results were reproduced at a reproduction power of 4 mW using a low-resolution pickup. See Figure 3.
図 1 3から、 反射層 6の膜厚が厚くなるほど、 超解像再生における C N Rが低 くなることがわかる。 実施例 3 (図 4の構造：析出促進層 7の効果） From Fig. 13, the CNR in super-resolution reproduction decreases as the thickness of the reflective layer 6 increases. It turns out that it becomes. Example 3 (Structure of FIG. 4: Effect of Precipitation-Promoting Layer 7)
実施例 1—1で作製したサンプルの第 1誘電体層 31と貴金属酸化物層 4との 間に、 析出促進層 7として厚さ 5nmの窒化ケィ素層を形成することにより、 図 4 に示す構造のサンプルを得た。 窒化ケィ素層は、 S iターゲットを A r ZN2= 8/2の流量比の混合ガス雰囲気中でスパッタリングすることにより形成した。 窒化ケィ素層の組成は S i3N4であった。 By forming a 5 nm-thick silicon nitride layer as the precipitation promoting layer 7 between the first dielectric layer 31 and the noble metal oxide layer 4 of the sample prepared in Example 1-1, as shown in FIG. A sample of the structure was obtained. Nitride Kei arsenide layer was formed by sputtering a S i target in a mixed gas atmosphere flow ratio of A r ZN 2 = 8/2. The composition of the silicon nitride layer was Si 3 N 4 .
このサンプルに記録パワー 1 OmWで、 配列ピッチ 40 Onm (マーク長 20 On m) の記録マーク列を記録し、 低分解能ピックアップを用いて再生したところ、 再生パワーが 3mWのときに最大の CNR 35dBが得られた。 一方、 実施例 1 _ 1 で作製したサンプルでは、 CNRが最大となる再生パワーは 4mWだったので、 析 出促進層 7を設けることにより、 再生感度が向上したことがわかる。 実施例 4 (図 5の構造：光吸収層 5を設けない構造）  A recording mark array with an array pitch of 40 Onm (mark length 20 On m) was recorded on this sample with a recording power of 1 OmW and reproduced using a low-resolution pickup.When the reproduction power was 3 mW, the maximum CNR of 35 dB was obtained. Obtained. On the other hand, in the sample prepared in Example 1-1, the reproduction power at which the CNR was maximized was 4 mW, which indicates that the provision of the precipitation promoting layer 7 improved the reproduction sensitivity. Example 4 (Structure of FIG. 5: Structure without light absorption layer 5)
図 5に示すように、 基板 2/第 1誘電体層 31Z貴金属酸化物層 4/第 2誘電 体層 32からなる積層構造を有する光ディスクサンプルを形成した。 このサンプ ルは、 実施例 1—1のサンプルから、 光吸収層 5および第 3誘電体層 33を取り 去った構造である。 ただし、 貴金属酸化物層 4の厚さは、 18^1または60^!1と した。  As shown in FIG. 5, an optical disc sample having a laminated structure composed of the substrate 2 / first dielectric layer 31Z noble metal oxide layer 4 / second dielectric layer 32 was formed. This sample has a structure in which the light absorption layer 5 and the third dielectric layer 33 are removed from the sample of Example 1-1. However, the thickness of the noble metal oxide layer 4 was set to 18 ^ 1 or 60 ^! 1.
貴金属酸化物層 4の厚さが 18 nmであるサンプルに、 5〜14mWの記録パワー で、 配列ピッチ 40 Onm (マーク長 20 Onm) の記録マーク列を記録し、 低分解 能ピックアップを用いて 4 mWの再生パヮ一で再生したところ、 CNRは得られな かった。 一方、 このサンプルに、 14mWの記録パワーで、 配列ピッチ 1. 6 μηι (マーク長 80 Onm) の記録マーク列を記録し、 4 mWの再生パワーで再生したと ころ、 34dBの CNRが得られた。 A recording mark array with an array pitch of 40 Onm (mark length 20 Onm) was recorded with a recording power of 5 to 14 mW on a sample with a thickness of the noble metal oxide layer 4 of 18 nm. When played back at mW playback speed, no CNR was obtained. On the other hand, a recording mark sequence with an array pitch of 1.6 μηι (mark length 80 Onm) was recorded on this sample at a recording power of 14 mW, and was reproduced with a reproduction power of 4 mW. At that time, a CNR of 34 dB was obtained.
また、 貴金属酸ィヒ物層 4の厚さが 6 Onmであるサンプルに対し、 7mWの記録パ ヮ一で、 配列ピッチ 40 Onm (マーク長 20 Onm) の記録マーク列を記録し、 低 分解能ピックアップを用いて 4mWの再生パワーで再生したところ、 12dBの CN Rが得られた。 一方、 このサンプルに、 7 mWの記録パワーで、 配列ピッチ 1. 6 μ ΐΆ (マーク長 80 Onm) の記録マーク列を記録し、 低分解能ピックアップを用 いて 4 mWの再生パワーで再生したところ、 33dBの CNRが得られた。  For a sample with a thickness of the noble metal oxide layer 4 of 6 Onm, a recording mark array with an array pitch of 40 Onm (mark length 20 Onm) was recorded at a recording power of 7 mW, and a low-resolution pickup When the data was reproduced with a reproduction power of 4 mW by using, a CNR of 12 dB was obtained. On the other hand, a recording mark array with an array pitch of 1.6 μΐΆ (mark length 80 Onm) was recorded on this sample with a recording power of 7 mW, and was reproduced with a reproduction power of 4 mW using a low-resolution pickup. A CNR of 33 dB was obtained.
この結果は、 光吸収層 5を設けなくても記録が可能であり、 かつ通常再生が可 能であることを示している。 したがって、 貴金属酸化物 4自体が記録層として機 能することがわかる。  This result indicates that recording is possible without providing the light absorption layer 5 and that normal reproduction is possible. Therefore, it is understood that the noble metal oxide 4 itself functions as a recording layer.
しかし、 貴金属酸化物層 4の厚さが 18 nmであるサンプルでは、 40 Onmのピ ツチ （記録マーク長 20 Onm) のマークの超解像再生が不可能であり、 前記した 再生メカニズムが働かなかったと考えられる。 一方、 貴金属酸ィ匕物層 4の厚さが 6 Onmのサンプルでは、 CNRは低いが超解像再生が可能である。  However, in the sample in which the thickness of the noble metal oxide layer 4 is 18 nm, super-resolution reproduction of a mark having a pitch of 40 Onm (recording mark length 20 Onm) is impossible, and the above-described reproduction mechanism does not work. It is considered that On the other hand, in the sample in which the thickness of the noble metal oxide layer 4 is 6 Onm, super resolution reproduction is possible although the CNR is low.
超解像再生において CNRが得られない、 あるいは低くなつたのは、 以下の理 由によると考えられる。 まず、 通常再生が可能であることから、 記録時には貴金 属層 4がレーザービームを吸収して昇温し、 Ag Oxが Agと 02とに分解して記 録マークが形成されたと考えられる。 し力 ^し、 記録後には貴金属酸化物層 4中に A gOxがほとんど存在せず、 媒体中にレーザービームの吸収を担う層がなくな つてしまったため、 再生用のレーザービームを照射しても貴金属酸化物層 4の昇 温が不十分となり、 A g粒子がほとんど析出しなレ、か、 十分には析出しなかった と考えられる。 貴金属酸化物層 4を厚くした場合に超解像再生が可能となったの は、 貴金属酸化物層 4の光吸収量が多くなったためと考えられる。 The reason why the CNR could not be obtained or became lower in super-resolution reproduction is considered to be as follows. First, since normal reproduction is possible, it is considered that during recording, the noble metal layer 4 absorbed the laser beam and rose in temperature, and Ag O x was decomposed into Ag and O 2 to form a recording mark. Can be After recording, there was almost no AgO x in the noble metal oxide layer 4 and there was no layer in the medium responsible for absorbing the laser beam. Also, it is considered that the temperature of the noble metal oxide layer 4 was insufficiently increased, and the Ag particles hardly precipitated or did not sufficiently precipitate. It is considered that super-resolution reproduction became possible when the noble metal oxide layer 4 was thickened because the amount of light absorption of the noble metal oxide layer 4 increased.

Claims

請求の範囲 The scope of the claims
1 . 光記録媒体に対し、 記録レーザービームを照射して記録マーク列を形成する ことにより記録を行い、 開口数 N Aの光学系を用いて波長; Iの再生レーザービー ムを照射して記録マーク列を読み出すことにより再生を行う方法であって、 光記録媒体は、 貴金属酸化物を含有する貴金属酸化物層を有し、 1. Recording is performed by irradiating an optical recording medium with a recording laser beam to form a series of recording marks, and irradiating a reproduction laser beam with a wavelength of I using an optical system with a numerical aperture of NA to record marks. A method for performing reproduction by reading a column, wherein the optical recording medium has a noble metal oxide layer containing a noble metal oxide,
記録マーク列は、 貴金属酸化物の分解によって貴金属酸化物層が変形すること により形成されたものであり、 マーク長が 0 . 3 7え/ N A未満である記録マー クを少なくとも含み、  The recording mark row is formed by deformation of the noble metal oxide layer due to decomposition of the noble metal oxide, and includes at least a recording mark having a mark length of less than 0.37 mm / NA.
記録マーク列が形成されている貴金属酸化物層におレ、て貴金属粒子を不可逆的 に析出させ、 析出した貴金属粒子に再生レーザービームを照射することにより記 録マーク列を読み出す光記録 Z再生方法。  Optical recording Z readout method in which noble metal particles are irreversibly deposited on the noble metal oxide layer on which the recording mark rows are formed, and the deposited noble metal particles are irradiated with a reproducing laser beam to read the recording mark rows. .
2 . 貴金属酸化物層に銀酸化物、 白金酸ィ匕物おょぴパラジウム酸ィ匕物の少なくと も 1種が含有される請求の範囲第 1項の光記録 Z再生方法。  2. The method for optical recording Z reproduction according to claim 1, wherein the noble metal oxide layer contains at least one of a silver oxide, a platinum oxide sulfide, and a palladium oxide.
3 . 光記録媒体が、 貴金属酸化物層を挟むように第 1誘電体層および第 2誘電体 層を有する請求の範囲第 1項の光記録/再生方法。 3. The optical recording / reproducing method according to claim 1, wherein the optical recording medium has a first dielectric layer and a second dielectric layer sandwiching the noble metal oxide layer.
4 . 光記録媒体が金属および Zまたは半金属を主成分とする光吸収層を有し、 光 吸収層と貴金属酸化物層とが第 2誘電体層を挟むように存在する請求の範囲第 3 項の光記録/再生方法。  4. The optical recording medium according to claim 3, wherein the optical recording medium has a light absorbing layer mainly composed of a metal and Z or a metalloid, and the light absorbing layer and the noble metal oxide layer are present so as to sandwich the second dielectric layer. Optical recording / reproducing method of item
5 . 光吸収層が少なくとも S bおよび/または T eを含有する請求の範囲第 4項 の光記録 Z再生方法。 5. The method according to claim 4, wherein the light absorbing layer contains at least Sb and / or Te.
6 . 光記録媒体が第 3誘電体層を有し、 第 3誘電体層と第 2誘電体層とが光吸収 層を挟むように存在する請求の範囲第 4項の光記録/再生方法。  6. The optical recording / reproducing method according to claim 4, wherein the optical recording medium has a third dielectric layer, and the third dielectric layer and the second dielectric layer are present so as to sandwich the light absorbing layer.
7 . 光記録媒体が金属および Zまたは半金属を主成分とする反射層を有し、 反射 層と光吸収層とが第 3誘電体層を挾むように存在する請求の範囲第 6項の光記録 ノ再生方法。 7. The optical recording device according to claim 6, wherein the optical recording medium has a reflective layer containing a metal and Z or a metalloid as a main component, and the reflective layer and the light absorbing layer are present so as to sandwich the third dielectric layer. No playback method.
8 . 貴金属酸化物を含有する貴金属酸ィヒ物層を有し、 前記貴金属酸化物が白金酸 化物および/またはパラジゥム酸化物である光記録媒体。  8. An optical recording medium having a noble metal oxide layer containing a noble metal oxide, wherein the noble metal oxide is a platinum oxide and / or a palladium oxide.
PCT/JP2003/007974 2002-06-24 2003-06-24 Optical recording/reproducing method and optical recording medium WO2004001735A1 (en)

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